VRS51x540 Datasheet Rev 1.2 Versa 8051 MCU with 4KB Flash Overview Feature Set The VRS51x540 is a low cost 8-bit microcontroller based on the standard 80C51 microcontroller family architecture. It is pin compatible and is a drop-in replacement for standard 8051 MCUs Aimed at cost effective applications requiring small amounts of program/data memory coupled with streamlined peripheral support, the VRS51x540 includes 4KB of Flash memory, 128 bytes of RAM a UART, three 16-bit timers, a Watchdog timer and power down features. The VRS51x540 is available in 5 (VRS51C540) and 3.3 (VRS51L540) volt versions in PLCC-44, QFP-44 and DIP-40 packages. The VRS51x540 devices operate over the entire industrial temperature range. The Flash memory can be programmed using programmers available from Ramtron or other 3rd party commercial programmers. * * * * * * * * * * * * * * * * * * * 80C51/80C52 pin compatible 12 clock periods per machine cycle 4KB on-chip Flash memory 128 bytes on-chip data RAM 32 I/O lines: P0-P3 = 8-bit Full duplex serial port (UART) 3, 16-bit Timers/Counters Watchdog Timer 8-bit Unsigned Division / Multiply BCD arithmetic Direct and Indirect Addressing Two levels of interrupt priority and nested interrupts Power saving modes Code protection function Operates at a clock frequency of up to 40MHz Low EMI (inhibit ALE) Programming voltage: 12V Industrial Temperature range (-40C to +85C) 5V and 3V versions available (see ordering information.) FIGURE 2: VRS51X540 PLCC AND QFP PINOUT DIAGRAMS 8051 PROCESSOR P1.5 ADDRESS/ DATA BUS 7 6 PORT 0 P0.3/AD3 P0.2/AD2 P0.1/AD1 P0.0/AD0 NC VDD 40 1 P0.4/AD4 39 P1.6 P0.5/AD5 P0.6/AD6 P1.7 RESET RXD/P3.0 4KB FLASH T2/P1.0 P1.2 T2EX/P1.1 P1.3 P1.4 FIGURE 1: VRS51X540 FUNCTIONAL DIAGRAM 8 P0.7/AD7 #EA VRS51x540 PLCC-44 NC TXD/P3.1 NC ALE #PSEN P2.7/A15 #INT0/P3.2 #INT1/P3.3 TIMER 0 P2.6/A14 P2.5/A13 P2.4/A12 P2.3/A11 P2.2/A10 #PSEN P2.7/A15 P2.1/A9 P2.0/A8 3 3 3 4 2 32 2 P0.0/AD0 VDD WATCHDOG TIMER P2.1/A9 P2.0/A8 VRS51x540 QFP-44 NC T2/P1.0 NC VSS T2EX/P1.1 P1.2 XTAL1 XTAL2 Ramtron International Corporation 1850 Ramtron Drive Colorado Springs Colorado, USA, 80921 ? ? ? #INT1/P3.3 TXD/P3.1 #INT0/P3.2 #RD/P3.7 #WR/P3.6 T0/P3.4 T1/P3.5 1 12 1 1 NC 4 4 RESET RXD/P3.0 P1.3 P1.4 P2.4/A12 P2.3/A11 P2.2/A10 P1.7 RESET P2.6/A14 P2.5/A13 29 P0.2/AD2 P0.1/AD1 P1.6 TIMER 2 P0.3/AD3 POWER CONTROL P1.5 TIMER 1 NC ALE 8 NC PORT 3 P0.7/AD7 #EA 2 INTERRUPT INPUTS VSS 8 XTAL2 XTAL1 PORT 2 28 #RD/P3.7 UART 17 18 #WR/P3.6 8 P0.5/AD5 P0.6/AD6 PORT 1 P0.4/AD4 T0/P3.4 T1/P3.5 128 Bytes of RAM http://www.ramtron.com MCU customer service: 1-800-943-4625, 1-514-871-2447, ext. 208 1-800-545-FRAM, 1-719-481-7000 page 1 of 40 VRS51x540 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 Bit 5 of Port 1 Bit 6 of Port 1 Bit 7 of Port 1 Reset Receive Data Bit 0 of Port 3 No Connect Transmit Data & Bit 1 of Port 3 External Interrupt 0 Bit 2 of Port 3 External Interrupt 1 Bit 3 of Port 3 Timer 0 Bit 4 of Port 3 Timer 1 & 3 Bit 5 of Port Ext. Memory Write Bit 6 of Port 3 Ext. Memory Read Bit 7 of Port 3 Oscillator/Crystal Output Oscillator/Crystal In Ground No Connect Bit 0 of Port 2 Bit 8 of External Memory Address Bit 1 of Port 2 Bit 9 of External Memory Address Bit 2 of Port 2 Bit 10 of External Memory Address Bit 3 of Port 2 & Bit 11 of External Memory Address Bit 4 of Port 2 Bit 12 of External Memory Address Bit 5 of Port 2 Bit 13 of External Memory Address 42 43 Bit 6 of Port 2 Bit 14 of External Memory Address Bit 7 of Port 2 Bit 15 of External Memory Address Program Store Enable Address Latch Enable No Connect External Access Bit 7 Of Port 0 Data/Address Bit 7 of External Memory Bit 6 of Port 0 Data/Address Bit 6 of External Memory Bit 5 of Port 0 Data/Address Bit 5 of External Memory Bit 4 of Port 0 Data/Address Bit 4 of External Memory Bit 3 Of Port 0 Data/Address Bit 3 of External Memory Bit 2 of Port 0 Data/Address Bit 2 of External Memory Bit 1 of Port 0 & Data Address Bit 1 of External Memory Bit 0 Of Port 0 & Data Address Bit 0 of External Memory VCC No Connect Timer 2 Clock Out Bit 0 of Port 1 Timer 2 Control Bit 1 of Port 1 Bit 2 of Port 1 Bit 3 of Port 1 44 P1.4 I/O Bit 4 of Port 1 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 P0.3/AD3 3 3 3 4 P2.6/A14 P2.5/A13 8 I/O I/O I/O I I I/O O I/O I I/O I I/O I I/O I I/O O I/O O I/O O I I/O O I/O O I/O O I/O O I/O O I/O O I/O O I/O O O O I I/O I/O I/O I/O I/O I/O I/O I/O I/O I/O I/O I/O I/O I/O I/O I/O I I/O I I/O I/O I/O P2.7/A15 7 P1.5 P1.6 P1.7 RES RXD P3.0 NC TXD P3.1 #INT0 P3.2 #INT1 P3.3 T0 P3.4 T1 P3.5 #WR P3.6 #RD P3.7 XTAL2 XTAL1 VSS NC P2.0 A8 P2.1 A9 P2.2 A10 P2.3 A11 P2.4 A12 P2.5 A13 P2.6 A14 P2.7 A15 #PSEN ALE NC #EA P0.7 AD7 P0.6 AD6 P0.5 AD5 P0.4 AD4 P0.3 AD3 P0.2 AD2 P0. 1 AD1 P0.0 AD0 VDD NC T2 P1.0 T2EX P1.1 P1.2 P1.3 24 #PSEN 6 Function Function NC ALE 5 I/O I/O P0.7/AD7 #EA 1 2 3 4 Name Name P0.6/AD6 QFP - 44 QFP - 44 P0.5/AD5 T ABLE 1: PIN DESCRIPTIONS FOR QFP-44/ P0.4/AD4 Pin Descriptions for QFP-44 2 32 2 P0.2/AD2 P0.1/AD1 P0.0/AD0 VDD P2.1/A9 P2.0/A8 VRS51x540 QFP-44 NC T2/P1.0 NC VSS T2EX/P1.1 P1.2 XTAL1 XTAL2 #INT1/P3.3 #INT0/P3.2 NC TXD/P3.1 RESET RXD/P3.0 P1.7 #RD/P3.7 #WR/P3.6 T0/P3.4 T1/P3.5 1 12 1 1 P1.6 4 4 P1.5 P1.3 P1.4 P2.4/A12 P2.3/A11 P2.2/A10 ________________________________________________________________________________________________ www.ramtron.com page 2 of 40 VRS51x540 Pin Descriptions for PLCC-44 14 15 16 17 18 19 20 21 22 23 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 I/O P0.6 I/O AD6 I/O P0.5 I/O AD5 I/O P0.4 I/O AD4 I/O P0.3 I/O AD3 I/O P0.2 I/O AD2 I/O P0. 1 AD1 P0.0 AD0 VDD I/O I/O I/O I/O - P1.4 44 AD7 P1.5 7 6 P0.3/AD3 13 26 P0.2/AD2 12 25 P0.1/AD1 11 24 P0.0/AD0 4 5 6 7 8 9 10 Function No Connect Timer 2 Clock Out Bit 0 of Port 1 Timer 2 Control Bit 1 of Port 1 Bit 2 of Port 1 Bit 3 of Port 1 Bit 4 of Port 1 Bit 5 of Port 1 Bit 6 of Port 1 Bit 7 of Port 1 Reset Receive Data Bit 0 of Port 3 No Connect Transmit Data & Bit 1 of Port 3 External Interrupt 0 Bit 2 of Port 3 External Interrupt 1 Bit 3 of Port 3 Timer 0 Bit 4 of Port 3 Timer 1 & 3 Bit 5 of Port Ext. Memory Write Bit 6 of Port 3 Ext. Memory Read Bit 7 of Port 3 Oscillator/Crystal Output Oscillator/Crystal In Ground No Connect VDD 3 I/O I I/O I I/O I/O I/O I/O I/O I/O I/O I I I/O O I/O I I/O I I/O I I/O I I/O O I/O O I/O O I - Function Bit 0 of Port 2 Bit 8 of External Memory Address Bit 1 of Port 2 Bit 9 of External Memory Address Bit 2 of Port 2 Bit 10 of External Memory Address Bit 3 of Port 2 & Bit 11 of External Memory Address Bit 4 of Port 2 Bit 12 of External Memory Address Bit 5 of Port 2 Bit 13 of External Memory Address Bit 6 of Port 2 Bit 14 of External Memory Address Bit 7 of Port 2 Bit 15 of External Memory Address Program Store Enable Address Latch Enable No Connect External Access Bit 7 Of Port 0 Data/Address Bit 7 of External Memory Bit 6 of Port 0 Data/Address Bit 6 of External Memory Bit 5 of Port 0 Data/Address Bit 5 of External Memory Bit 4 of Port 0 Data/Address Bit 4 of External Memory Bit 3 Of Port 0 Data/Address Bit 3 of External Memory Bit 2 of Port 0 Data/Address Bit 2 of External Memory Bit 1 of Port 0 & Data Address Bit 1 of External Memory Bit 0 Of Port 0 & Data Address Bit 0 of External Memory VCC NC 2 Name NC T2 P1.0 T2EX P1.1 P1.2 P1.3 P1.4 P1.5 P1.6 P1.7 RES RXD P3.0 NC TXD P3.1 #INT0 P3.2 #INT1 P3.3 T0 P3.4 T1 P3.5 #WR P3.6 #RD P3.7 XTAL2 XTAL1 VSS NC I/O I/O O I/O O I/O O I/O O I/O O I/O O I/O O I/O O O O I I/O T2/P1.0 1 Name P2.0 A8 P2.1 A9 P2.2 A10 P2.3 A11 P2.4 A12 P2.5 A13 P2.6 A14 P2.7 A15 #PSEN ALE NC #EA P0.7 P1.2 T2EX/P1.1 PLCC - 44 P1.3 PLCC - 44 T ABLE 2: PIN DESCRIPTIONS FOR PLCC-44 40 1 39 P1.6 RESET RXD/P3.0 P0.7/AD7 #EA VRS51x540 PLCC-44 NC TXD/P3.1 #INT0/P3.2 NC ALE #PSEN P2.7/A15 #INT1/P3.3 17 18 29 P2.6/A14 P2.5/A13 P2.4/A12 P2.3/A11 P2.2/A10 P2.1/A9 NC VSS P2.0/A8 XTAL1 XTAL2 28 #RD/P3.7 #WR/P3.6 T0/P3.4 T1/P3.5 P0.4/AD4 P0.5/AD5 P0.6/AD6 P1.7 ________________________________________________________________________________________________ www.ramtron.com page 3 of 40 VRS51x540 VRS51x540 DIP-40 Pin Descriptions T ABLE 3: VRS51X540 IN DESCRIPTIONS FOR DIP-40 PACKAGE DIP40 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Name I/O T2 P1.0 T2EX P1.1 P1.2 P1.3 P1.4 P1.5 P1.6 P1.7 RESET RXD P3.0 TXD P3.1 #INT0 P3.2 #INT1 P3.3 T0 P3.4 T1 P3.5 #WR P3.6 #RD P3.7 XTAL2 XTAL1 VSS I I/O I I/O I/O I/O I/O I/O I/O I/O I I I/O O I/O I I/O I I/O I I/O I I/O O I/O O I/O O I - Function Timer 2 Clock Out Bit 0 of Port 1 Timer 2 Control Bit 1 of Port 1 Bit 2 of Port 1 Bit 3 of Port 1 Bit 4 of Port 1 Bit 5 of Port 1 Bit 6 of Port 1 Bit 7 of Port 1 Reset Receive Data Bit 0 of Port 3 Transmit Data & Bit 1 of Port 3 External Interrupt 0 Bit 2 of Port 3 External Interrupt 1 Bit 3 of Port 3 Timer 0 Bit 4 of Port 3 Timer 1 & 3 Bit 5 of Port Ext. Memory Write Bit 6 of Port 3 Ext. Memory Read Bit 7 of Port 3 Oscillator/Crystal Output Oscillator/Crystal In Ground T2 / P1.0 1 40 VDD T2EX / P1.1 2 39 P0.0 / AD0 P1.2 3 38 P0.1 / AD1 P1.3 4 37 P0.2 / AD2 P1.4 5 36 P0.3 / AD3 P1.5 6 35 P0.4 / AD4 P1.6 7 34 P0.5 / AD5 P1.7 8 33 P0.6 / AD6 RESET 9 32 P0.7 / AD7 31 #EA / VPP RXD / P3.0 10 VRS51x540 DIP-40 TXD / P3.1 11 30 ALE #INT0 / P3.2 12 29 PSEN #INT1 / P3.3 13 28 P2.7 / A15 T0 / P3.4 14 27 P2.6 / A14 T1 / P3.5 15 26 P2.5 / A13 #WR / P3.6 16 25 P2.4 / A12 #RD / P3.7 17 24 P2.3 / A11 XTAL2 18 23 P2.2 / A10 XTAL1 19 22 P2.1 / A9 VSS 20 21 P2.0 / A8 DIP40 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 Name I/O P2.0 A8 P2.1 A9 P2.2 A10 P2.3 A11 P2.4 A12 P2.5 A13 P2.6 A14 P2.7 A15 #PSEN ALE #EA / VPP P0.7 I/O O I/O O I/O O I/O O I/O O I/O O I/O O I/O O O O AD7 I/O P0.6 I/O AD6 I/O P0.5 I/O AD5 I/O P0.4 I/O AD4 I/O P0.3 I/O AD3 I/O P0.2 I/O AD2 I/O P0. 1 AD1 P0.0 AD0 VDD I/O I/O I/O I/O - I I/O Function Bit 0 of Port 2 Bit 8 of External Memory Address Bit 1 of Port 2 Bit 9 of External Memory Address Bit 2 of Port 2 Bit 10 of External Memory Address Bit 3 of Port 2 & Bit 11 of External Memory Address Bit 4 of Port 2 Bit 12 of External Memory Address Bit 5 of Port 2 Bit 13 of External Memory Address Bit 6 of Port 2 Bit 14 of External Memory Address Bit 7 of Port 2 Bit 15 of External Memory Address Program Store Enable Address Latch Enable External Access Flash programming voltage input Bit 7 Of Port 0 Data/Address Bit 7 of External Memory Bit 6 of Port 0 Data/Address Bit 6 of External Memory Bit 5 of Port 0 Data/Address Bit 5 of External Memory Bit 4 of Port 0 Data/Address Bit 4 of External Memory Bit 3 Of Port 0 Data/Address Bit 3 of External Memory Bit 2 of Port 0 Data/Address Bit 2 of External Memory Bit 1 of Port 0 & Data Address Bit 1 of External Memory Bit 0 Of Port 0 & Data Address Bit 0 of External Memory Supply input ______________________________________________________________________________________________ www.ramtron.com page 4 of 40 VRS51x540 Instruction Set Mnemonic The following tables describe the instruction set of the VRS51x540. The instructions are functional and binary code compatible with industry standard 8051s. T ABLE 4: LEGEND FOR INSTRUCTION SET T ABLE Symbol A Rn Direct @Ri Rel Bit #data #data 16 addr 16 addr 11 Function Accumulator Register R0-R7 Internal register address Internal register pointed to by R0 or R1 (except MOVX) Two's complement offset byte Direct bit address 8-bit constant 16-bit constant 16-bit destination address 11-bit destination address T ABLE 5: VRS51X540 INSTRUCTION SET Mnemonic Description Arithmetic instructions ADD A, Rn Add register to A ADD A, direct Add direct byte to A ADD A, @Ri Add data memory to A ADD A, #data Add immediate to A ADDC A, Rn Add register to A with carry ADDC A, direct Add direct byte to A with carry ADDC A, @Ri Add data memory to A with carry ADDC A, #data Add immediate to A with carry SUBB A, Rn Subtract register from A with borrow SUBB A, direct Subtract direct byte from A with borrow SUBB A, @Ri Subtract data mem from A with borrow SUBB A, #data Subtract immediate from A with borrow INC A Increment A INC Rn Increment register INC direct Increment direct byte INC @Ri Increment data memory DEC A Decrement A DEC Rn Decrement register DEC direct Decrement direct byte DEC @Ri Decrement data memory INC DPTR Increment data pointer MUL AB Multiply A by B DIV AB Divide A by B DA A Decimal adjust A Logical Instructions ANL A, Rn AND register to A ANL A, direct AND direct byte to A ANL A, @Ri AND data memory to A ANL A, #data AND immediate to A ANL direct, A AND A to direct byte ANL direct, #data AND immediate data to direct byte ORL A, Rn OR register to A ORL A, direct OR direct byte to A ORL A, @Ri OR data memory to A ORL A, #data OR immediate to A ORL direct, A OR A to direct byte ORL direct, #data OR immediate data to direct byte XRL A, Rn Exclusive-OR register to A XRL A, direct Exclusive-OR direct byte to A XRL A, @Ri Exclusive-OR data memory to A XRL A, #data Exclusive-OR immediate to A XRL direct, A Exclusive-OR A to direct byte XRL direct, #data Exclusive-OR immediate to direct byte CLR A Clear A CPL A Compliment A SWAP A Swap nibbles of A RL A Rotate A left RLC A Rotate A left through carry RR A Rotate A right RRC A Rotate A right through carry Size (bytes) Instr. Cycles 1 2 1 2 1 2 1 2 1 2 1 2 1 1 2 1 1 1 2 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 4 4 1 1 2 1 2 2 3 1 2 1 2 2 3 1 2 1 2 2 3 1 1 1 1 1 1 1 1 1 1 1 1 2 1 1 1 1 1 2 1 1 1 1 1 2 1 1 1 1 1 1 1 Description Boolean Instruction CLR C Clear Carry bit CLR bit Clear bit SETB C Set Carry bit to 1 SETB bit Set bit to 1 CPL C Complement Carry bit CPL bit Complement bit ANL C,bit Logical AND between Carry and bit ANL C,#bit Logical AND between Carry and not bit ORL C,bit Logical ORL between Carry and bit ORL C,#bit Logical ORL between Carry and not bit MOV C,bit Copy bit value into Carry MOV bit,C Copy Carry value into Bit Data Transfer Instructions MOV A, Rn Move register to A MOV A, direct Move direct byte to A MOV A, @Ri Move data memory to A MOV A, #data Move immediate to A MOV Rn, A Move A to register MOV Rn, direct Move direct byte to register MOV Rn, #data Move immediate to register MOV direct, A Move A to direct byte MOV direct, Rn Move register to direct byte MOV direct, direct Move direct byte to direct byte MOV direct, @Ri Move data memory to direct byte MOV direct, #data Move immediate to direct byte MOV @Ri, A Move A to data memory MOV @Ri, direct Move direct byte to data memory MOV @Ri, #data Move immediate to data memory MOV DPTR, #data Move immediate to data pointer MOVC A, @A+DPTR Move code byte relative DPTR to A MOVC A, @A+PC Move code byte relative PC to A MOVX A, @Ri Move external data (A8) to A MOVX A, @DPTR Move external data (A16) to A MOVX @Ri, A Move A to external data (A8) MOVX @DPTR, A Move A to external data (A16) PUSH direct Push direct byte onto stack POP direct Pop direct byte from stack XCH A, Rn Exchange A and register XCH A, direct Exchange A and direct byte XCH A, @Ri Exchange A and data memory XCHD A, @Ri Exchange A and data memory nibble Branching Instructions ACALL addr 11 Absolute call to subroutine LCALL addr 16 Long call to subroutine RET Return from subroutine RETI Return from interrupt AJMP addr 11 Absolute jump unconditional LJMP addr 16 Long jump unconditional SJMP rel Short jump (relative address) JC rel Jump on carry = 1 JNC rel Jump on carry = 0 JB bit, rel Jump on direct bit = 1 JNB bit, rel Jump on direct bit = 0 JBC bit, rel Jump on direct bit = 1 and clear JMP @A+DPTR Jump indirect relative DPTR JZ rel Jump on accumulator = 0 JNZ rel Jump on accumulator 1= 0 CJNE A, direct, rel Compare A, direct JNE relative CJNE A, #d, rel Compare A, immediate JNE relative CJNE Rn, #d, rel Compare reg, immediate JNE relative CJNE @Ri, #d, rel Compare ind, immediate JNE relative DJNZ Rn, rel Decrement register, JNZ relative DJNZ direct, rel Decrement direct byte, JNZ relative Miscellaneous Instruction NOP No operation Rn: Any of the register R0 to R7 @Ri: Indirect addressing using Register R0 or R1 #data: immediate Data provided with Instruction #data16: Immediate data included with instruction bit: address at the bit level rel: relative address to Program counter from +127 to -128 Addr11: 11-bit address range Addr16: 16-bit address range #d: Immediate Data supplied with instruction Size (bytes) Instr. Cycles 1 2 1 2 1 2 2 2 2 2 2 2 1 1 1 1 1 1 2 2 2 2 1 2 1 2 1 2 1 2 2 2 2 3 2 3 1 2 2 3 1 1 1 1 1 1 2 2 1 2 1 1 1 1 1 1 1 2 1 1 2 2 2 2 1 2 1 2 2 2 2 2 2 2 2 2 1 1 1 1 2 3 1 1 2 3 2 2 2 3 3 3 1 2 2 3 3 3 3 2 3 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 1 1 ______________________________________________________________________________________________ www.ramtron.com page 5 of 40 VRS51x540 Special Function Registers (SFR) Addresses 80h to FFh of the SFR address space can be accessed in direct addressing mode only. The following table lists the VRS51x540 Special Function Registers. T ABLE 6: SPECIAL FUNCTION REGISTERS (SFR) SFR Register P0 SP DPL DPH Reserved PCON TCON TMOD TL0 TL1 TH0 TH1 P1 SCON SBUF WDTCON P2 IE P3 IP SYSCON T2CON RCAP2L RCAP2H TL2 TH2 PSW ACC B SFR Adrs 80h 81h 82h 83h 84h 87h 88h 89h 8Ah 8Bh 8Ch 8Dh 90h 98h 99h 9Fh A0h A8h B0h B8h BFh C8h CAh CBh CCh CDh D0h E0h F0h Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 SMOD TF1 GATE1 SM0 WDTE EA WDRESET TF2 - TR1 C/T1 SM1 EXF2 - TF0 M1.1 SM2 WDCLR ET2 PT2 RCLK - TR0 M0.1 REN ES PS TCLK - GF1 IE1 GATE0 TB8 ET1 PT1 EXEN2 - GF0 IT1 C/T0 RB8 WDPS2 EX1 PX1 PDOWN IE0 M1.0 TI WDPS1 ET0 PT0 TR2 - C/T2 - IDLE IT0 M0.0 RI WDPS0 EX0 PX0 ALEI CP/RL2 - CY - AC - F0 - RS1 - RS0 - OV - - P - Reset Value 00000000b 00000000b 00000000b 00000000b 0*0**000b 00000000b 00000000b 0*****00b 00000000b 00000000b 00000000b 00000000b 00000000b 00000000b ______________________________________________________________________________________________ www.ramtron.com page 6 of 40 VRS51x540 Program Memory Structure Data Memory Program Memory The VRS51x540 includes 4k of on-chip Program Flash memory. The VRS51x540 has a total of 128 Bytes of RAM memory configured as the internal memory structure of a standard 8051. FIGURE 4: VRS51X540 DATA MEMORY FIGURE 3: VRS51X540 INTERNAL PROGRAM MEMORY FFFh FFh 80h 7Fh VRS51x540 Flash Memory (4K Bytes) 00h 0000h Program Status Word Register The PSW register is a bit addressable register that contains the status flags (CY, AC, OV, P), user flag (F0) and register bank select bits (RS1, RS0) of the 8051 processor. T ABLE 7: PROGRAM STATUS WORD REGISTER (PSW) - SFR DOH 7 CY Bit 7 6 5 4 3 2 1 0 RS1 0 0 1 1 6 AC 5 F0 Mnemonic CY AC F0 RS1 RS0 OV P RS0 0 1 0 1 4 RS1 3 RS0 2 OV 1 - 0 P Description Carry Bit Auxiliary Carry Bit from bit 3 to 4. User flag R0-R7 Registers bank select bit 0 R0-R7 Registers bank select bit 1 Overflow flag Parity flag Active Bank 0 1 2 3 Address 00h-07h 08h-0Fh 10h-17h 18-1Fh 128 bytes RAM (indirect addressing only) 128 bytes RAM (Can be accessed in indirect and direct addressing mode) Lower 128 bytes (00h to 7Fh, Bank 0 & Bank 1) The lower 128 bytes of data memory (from 00h to 7Fh) is summarized as follows: * Address range 00h to 7Fh can be accessed in direct and indirect addressing modes. * Address range 00h to 1Fh includes R0-R7 registers area. * Address range 20h to 2Fh is bit addressable. * Address range 30h to 7Fh is not bit addressable and can be used as general-purpose storage. . FIGURE 5: VRS51X540 INTERNAL RAM STRUCTURE FFh SFR Area Direct or Bit Access Only DPH DPL SP P0 The VRS51x540 has one 16-bit data pointer. The DPTR is accessed through two SFR addresses: DPL located at address 82h and DPH located at address 83h. 87 86 85 84 83 82 81 80 80h 7Fh 80 Bytes of General Purpose RAM 30h 2Fh 20h Data Pointer SFR (Direct addressing mode only) 18h 10h 08h 00h 7F 7E 7D 7C 7B 7A 79 78 77 76 75 74 73 72 71 70 0F 0E 0D 0C 0B 0A 09 08 07 06 05 04 03 02 01 00 R7 R0 R7 R0 R7 R0 R7 R0 Registers Bank 3 Registers Bank 2 Registers Bank 1 Registers Bank 0 ______________________________________________________________________________________________ www.ramtron.com page 7 of 40 VRS51x540 These power saving modes are controlled by the PDOWN and IDLE bits of the PCON register at address 87h. Description of Peripherals System Control Register The SYSCON Register is used for system control and is described in the following table. The WDRESET bit (7) indicates whether the system has been reset due to the overflow of the Watchdog Timer. Bit 0 of the SYSCON register is the ALE output inhibit bit. Setting this bit to a 1 will inhibit the Fosc/6 clock signal output to the ALE pin. T ABLE 9: POWER CONTROL REGISTER (PCON) - SFR 87H 7 Bit 7 6 Mnemonic SMOD 7 6 5 Bit 7 Mnemonic 6 5 4 3 2 1 0 Unused Unused Unused Unused Unused Unused ALEI WDRESET 4 3 Unused 2 1 XRAME 0 ALEI Description This is the Watchdog Timer reset bit. It will be set to 1 when the reset signal generated by WDT overflows. ALE output inhibit bit, which is used to reduce EMI. 3 2 1 RAM1 0 RAM0 Description 1: Double the baud rate of the serial port frequency that was generated by Timer 1. 0: Normal serial port baud rate generated by Timer 1. T ABLE 8: SYSTEM CONTROL REGISTER (SYSCON) - SFR BFH WDRESET 5 4 Unused 6 5 4 3 2 1 0 GF1 GF0 PDOWN IDLE General Purpose Flag General Purpose Flag Power down mode control bit Idle mode control bit Power Control Register The VRS51x540 provides two power saving modes: Idle and Power Down. These two modes serve to reduce the power consumption of the device. In Idle mode, the processor is stopped but the oscillator continues to run. The content of the RAM, I/O state and SFR registers are maintained and the Timer and external interrupts are left operational. The processor will be woken up when an external event, triggering an interrupt, occurs. In Power Down mode, the oscillator and peripherals of the VRS51x540 are disabled. The contents of the RAM and the SFR registers, however, are maintained. The minimum VCC in Power Down mode is 2V. ______________________________________________________________________________________________ www.ramtron.com page 8 of 40 VRS51x540 Input/Output Ports The VRS51x540 has a total of 32 bi-directional I/O lines grouped into four 8-bit I/O ports. These I/Os can be individually configured as inputs or outputs. FIGURE 6: INTERNAL STRUCTURE OF ONE OF THE FOUR I/O PORT LINES Read Register With the exception of the P0 I/Os, which are of the open drain type, each I/O is made of a transistor connected to ground and a weak pull-up resistor. Internal Bus Writing a 0 in a given I/O port bit register will activate the transistor connected to Vss, this will bring the I/O to a LOW level. Writing a 1 into a given I/O port bit register de-activates the transistor between the pin and ground. In this case the pull-up resistor will bring the corresponding pin to a HIGH level. To use a given I/O as an input, a 1 must be written into its associated port register bit. By default, upon reset all I/Os are configured as inputs. General Structure of an I/O Port The following elements establish the link between the core unit and the pins of the microcontroller: * Special Function Register (same name as port) * Output Stage Amplifier (the structure of this element varies with its auxiliary function) From the next figure, one can see that the D flip-flop stores the value received from the internal bus after receiving a write signal from the core. Also, note that the Q output of the flip-flop can be linked to the internal bus by executing a read instruction. This is how one would read the content of the register. It is also possible to link the value of the pin to the internal bus. This is done by the "read pin" instruction. In short, the user may read the value of the register or the pin. Q D Flip-Flop Write to Register Output Stage IC Pin Q Read Pin Structure of the P1, P2, P3 The following figure gives a general idea of the structure P1, P2 and P3 ports. Note that the figure below does not show the intermediary logic that connects the output of the register and the output stage together because this logic varies with the auxiliary function of each port. FIGURE 7: GENERAL STRUCTURE OF THE O UTPUT STAGE OF P1, P2 AND P3 Read Register Vcc Pull-up Network Internal Bus Q IC Pin D Flip-Flop Write to Register Q X1 Read Pin Each line may be used independently as a logical input or output. When used as an input, as mentioned earlier, the corresponding port register bit must be high. ______________________________________________________________________________________________ www.ramtron.com page 9 of 40 VRS51x540 Structure of Port 0 Port P0 and P2 as Address and Data Bus The internal structure of P0 is shown below. The auxiliary function of this port requires a particular logic. As opposed to the other ports, P0 is truly bi-directional. In other words, when used as an input, it is considered to be in a floating logical state (high impedance state). This arises from the absence of the internal pull-up resistance. The pull-up resistance is actually replaced by a transistor that is only used when the port is configured to access the external memory/data bus (EA=0). The output stage may receive data from two sources When used as an I/O port, P0 acts as an open drain port and the use of an external pull-up resistor is likely to be required for most applications. * The outputs of register P0 or the bus address itself, multiplexed with the data bus for P0. * The outputs of the P2 register or the high byte (A8 through A15) of the bus address for the P2 port. FIGURE 9: P2 PORT STRUCTURE Read Register Vcc Address Pull-up Network FIGURE 8: PORT P0' S PARTICULAR STRUCTURE Q Internal Bus IC Pin D Flip-Flop Address A0/A7 Read Register Write to Register Control X1 Q Control Vcc Internal Bus Read Pin Q IC Pin D Flip-Flop Write to Register Q X1 Read Pin When P0 is used as an external memory bus input (for a MOVX instruction, for example), the outputs of the register are automatically forced to 1. When the ports are used as an address or data bus, the special function registers P0 and P2 are disconnected from the output stage. The 8-bits of the P0 register are forced to 1 and the content of the P2 register remains constant. Auxiliary Port 1 Functions The port 1 I/O pins are shared with the Timer 2 EX and T2 inputs as shown below: Pin P1.0 P1.1 P1.2 Mnemonic T2 T2EX Function Timer 2 counter input Timer2 Auxiliary input P1.3 P1.4 P1.5 P1.6 P1.7 ______________________________________________________________________________________________ www.ramtron.com page 10 of 40 VRS51x540 Auxiliary P3 Port Functions Software Particularities Concerning the Ports The Port 3 I/O pins are shared with the UART interface, INT0 and INT1 interrupts, Timer 0 and Timer 1 inputs and finally the #WR and #RD lines when external memory access is performed. Some instructions allow the user to read the logic state of the output pin, while others allow the user to read the content of the associated port register. These instructions are called read-modify-write instructions. A list of these instructions may be found in the table below. FIGURE 10: P3 PORT STRUCTURE Auxiliary Function: Output Read Register Vcc IC Pin Q Internal Bus X1 D Flip-Flop Write to Register Q Read Pin Auxiliary Function: Input The following table describes the auxiliary function of the port 3 I/O pins. T ABLE 10: P3 AUXILIARY F UNCTION T ABLE Pin P3.0 P3.1 P3.2 P3.3 Mnemonic RXD TXD INT0 INT1 P3.4 P3.5 P3.6 T0 T1 P3.7 RD WR Function Serial Port: Receive data in asynchronous mode. Input and output data in synchronous mode. Serial Port: Transmit data in asynchronous mode. Output clock value in synchronous mode. External Interrupt 0 Timer 0 Control Input External Interrupt 1 Timer 1 Control Input Timer 0 Counter Input Timer 1 Counter Input Write signal for external memory Read signal for external memory Upon execution of these instructions, the content of the port register (at least 1-bit) is modified. The other read instructions take the present state of the input into account. For example, the instruction ANL P3, #01h obtains the value in the P3 register; performs the desired logic operation with the constant 01h; and recopies the result into the P3 register. When users want to take the present state of the inputs into account, they must first read these states and perform an AND operation between the reading and the constant. MOV A, P3; State of the inputs in the accumulator ANL A, #01; AND operation between P3 and 01h When the port is used as an output, the register contains information on the state of the output pins. Measuring the state of an output directly on the pin is inaccurate because the electrical level depends mostly on the type of charge that is applied to it. The functions shown below take the value of the register rather than that of the pin. T ABLE 11: LIST OF INSTRUCTIONS THAT READ AND MODIFY THE PORT USING REGISTER VALUES Instruction ANL ORL XRL JBC CPL INC DEC DJNZ MOV P., C CLR P.x SETB P.x Function Logical AND ex: ANL P0, A Logical OR ex: ORL P2, #01110000B Exclusive OR ex: XRL P1, A Jump if the bit of the port is set to 0 Complement one bit of the port Increment the port register by 1 Decrement the port register by 1 Decrement by 1 and jump if the result is not equal to 0 Copy the held bit C to the port Set the port bit to 0 Set the port bit to 1 ______________________________________________________________________________________________ www.ramtron.com page 11 of 40 VRS51x540 Port Operation Timing Writing to a Port (Output) When an operation results in a modification of the content in a port register, the new value is placed at the output of the D flip-flop during the T12 period of the last machine cycle that the instruction needed to execute. It is important to note, however, that the output stage only samples the output of the registers on the P1 phase of each period. It follows the new value appearing at the output after the T12 period of the following machine cycle. Reading a Port (Input) The reading of an I/O pin takes place: * During T9 cycle for P0, P1 * During T10 cycle for P2, P3 * When the ports are configured as I/Os * In order to be sampled, the signal duration present on the I/O inputs must be longer than Fosc/12. I/O Ports Driving Capability The maximum allowable continuous current that the device can sink on an I/O port is defined by the following: Maximum sink current on one given I/O Maximum total sink current for P0 Maximum total sink current for P1, 2, 3 Maximum total sink current on all I/O 10mA 26mA 15mA 71mA It is not recommended to exceed the sink current outlined in the above table. Doing so is likely to make the low-level output voltage exceed the device's specification and it is likely to affect device reliability. The VRS51x540 I/O ports are not designed to source current. ______________________________________________________________________________________________ www.ramtron.com page 12 of 40 VRS51x540 Timers The VRS51x540 includes three 16-bit timers: T0, T1 and T2. The timers can operate in two specific modes: * Event counting mode * Timer mode When operating in counting mode, the counter is incremented each time an external event, such as a transition in the logical state of the timer input (T0, T1, T2 input), is detected. When operating in timer mode, the counter is incremented by the microcontroller's direct clock pulse or by a divided version of this pulse. Timer 0 and Timer 1 Timers 0 and 1 have four modes of operation. These modes allow the user to change the size of the counting register or to authorize an automatic reload when provided with a specific value. Timer 1 can also be used as a baud rate generator to generate communication frequencies for the serial interface. Timer 1 and Timer 0 are configured by the TMOD and TCON registers. T ABLE 12: T IMER MODE CONTROL REGISTER (TMOD) - SFR 89H 7 GATE 6 C/T 5 M1 Bit 7 Mnemonic GATE1 6 C/T1 5 4 3 M1.1 M0.1 GATE0 2 C/T0 1 0 M1.0 M0.0 4 M0 3 GATE 2 C/T 1 M1.0 0 M0.0 Description 1: Enables external gate control (pin INT1 for Counter 1). When INT1 is high, and TRx bit is set (see TCON register), a counter is incremented every falling edge on the T1IN input pin. Selects timer or counter operation (Timer 1). 1 = A counter operation is performed 0 = The corresponding register will function as a timer. Selects mode for Timer/Counter 1 Selects mode for Timer/Counter 1 If set, enables external gate control (pin INT0 for Counter 0). When INT0 is high, and TRx bit is set (see TCON register), a counter is incremented every falling edge on the T0IN input pin. Selects timer or counter operation (Timer 0). 1 = A counter operation is performed 0 = The corresponding register will function as a timer. Selects mode for Timer/Counter 0. Selects mode for Timer/Counter 0. The table below summarizes the four modes of operation of timers 0 and 1. The timer-operating mode is selected by the bits M1 and M0 of the TMOD register. T ABLE 13: T IMER/COUNTER MODE DESCRIPTION SUMMARY M1 M0 Mode Function 0 0 1 0 1 0 Mode 0 Mode 1 Mode 2 1 1 Mode 3 13-bit Counter 16-bit Counter 8-bit auto-reload Counter/Timer. The reload value is kept in TH0 or TH1, while TL0 or TL1 is incremented every machine cycle. When TLx overflows, the value of THx is copied to TLx. If Timer 1 M1 and M0 bits are set to 1, Timer 1 stops. ______________________________________________________________________________________________ www.ramtron.com page 13 of 40 VRS51x540 Timer 0/ Timer 1 Counter / Timer Functions Operating Modes Timing Function The user may change the operating mode by varying the M1 and M0 bits of the TMOD SFR. When operating as a timer, the counter is automatically incremented at every system cycle (Fosc/12). A flag is raised in the event that an overflow occurs and the counter acquires a value of zero. These flags (TF0 and TF1) are located in the TCON register. T ABLE 14: T IMER 0 AND 1 CONTROL REGISTER (TCON) -SFR 88H 7 6 5 4 3 2 1 0 TF1 TR1 TF0 TR0 IE1 IT1 IE0 IT0 Bit 7 Mnemonic TF1 Description Timer 1 Overflow Flag. Set by hardware on Timer/Counter overflow. Cleared by hardware on Timer/Counter overflow. Cleared by hardware when processor vectors to interrupt routine. 6 TR1 5 TF0 Timer 1 Run Control Bit. Set/cleared by software to turn Timer/Counter on or off. Timer 0 Overflow Flag. Set by hardware on Timer/Counter overflow. Cleared by hardware when processor vectors to interrupt routine. Timer 0 Run Control Bit. Set/cleared by software to turn Timer/Counter on or off. Interrupt Edge Flag. Set by hardware when external interrupt edge is detected. Cleared when interrupt processed. Interrupt 1 Type Control Bit. Set/cleared by software to specify falling edge/low level triggered external interrupts. Interrupt 0 Edge Flag. Set by hardware when external interrupt edge is detected. Cleared when interrupt processed. Interrupt 0 Type control bit. Set/cleared by software to specify falling edge/low level triggered external interrupts. 4 TR0 3 IE1 2 IT1 1 IE0 0 IT0 Counting Function When operating as a counter, the timer's register is incremented at every falling edge of the T0, T1 and T2 signals located at the input of the timer. In this case, the signal is sampled at the T10 phase of each machine cycle for Timer 0, Timer 1 and T9 for Timer 2. When the sampler sees a high immediately followed by a low in the next machine cycle, the counter is incremented. Two system cycles are required to detect and record an event. This reduces the counting frequency by a factor of 24 (24 times less than the oscillator's frequency). Mode 0 A schematic representation of this mode of operation can be found in Figure 11. From the figure, we notice that the timer operates as an 8-bit counter preceded by a divide-by-32 prescaler composed of the 5 LSBs of TL1. The register of the counter is configured to be 13 bits long. When an overflow causes the value of the register to roll over to 0, the TFx interrupt signal goes to 1. The count value is validated as soon as TRx goes to 1 and the GATE bit is 0, or when INTx is 1. FIGURE 11: T IMER/COUNTER 1 MODE 0: 13-BIT COUNTER CLK /12 0 TL1 C/T =0 CLK 1 T1PIN 0 4 7 Mode 0 C/T =1 Control Mode 1 TR1 GATE 0 TH1 7 INT1 PIN TF1 INT Mode 1 Mode 1 is almost identical to Mode 0. They differ in that in Mode 1, the counter uses the full 16-bits and has no prescaler. Mode 2 In this mode, the register of the timer is configured as an 8-bit automatically re-loadable counter. In Mode 2, it is the lower byte TLx that is used as the counter. In the event of a counter overflow, the TFx flag is set to 1 and the value contained in THx, which is preset by software, is reloaded into the TLx counter. The value of THx remains unchanged. ______________________________________________________________________________________________ www.ramtron.com page 14 of 40 VRS51x540 FIGURE 12: T IMER/COUNTER 1 MODE 2: 8-BIT AUTOMATIC RELOAD CLK /12 0 C/T =0 1 C/T=1 TL1 0 7 Control T1 Pin Reload 0 7 TH1 TR1 GATE TF1 INT INT0 PIN Mode 3 In Mode 3, Timer 1 is blocked as if its control bit, TR1, was set to 0. In this mode, Timer 0's registers TL0 and TH0 are configured as two separate 8-bit counters. Also, the TL0 counter uses Timer 0's control bits C/T, GATE, TR0, INT0, TF0 and the TH0 counter is held in Timer Mode (counting machine cycles) and gains control over TR1 and TF1 from Timer 1. At this point, TH0 controls the Timer 1 interrupt. FIGURE 13: T IMER/COUNTER 0 MODE 3 TH0 CLK 0 7 Control TF1 TR1 CLK 0 TL0 C/T =0 CLK 1 T0PIN INTERRUPT /12 0 7 C/T =1 Control TF0 INTERRUPT TR0 GATE INT0 PIN ______________________________________________________________________________________________ www.ramtron.com page 15 of 40 VRS51x540 0 Timer 2 Timer 2 of the VRS51x540 is a 16-bit Timer/Counter. Similar to timers 0 and 1, Timer 2 can operate either as an event counter or as a timer. The user may switch functions by writing to the C/T2 bit located in the T2CON special function register. Timer 2 has three operating modes: "Auto-Load" "Capture", and "Baud Rate Generator". The T2CON SFR configures the modes of operation of Timer 2. The following table describes each bit in the T2CON special function register. T ABLE 15: T IMER 2 CONTROL REGISTER (T2CON) -SFR C8H 7 6 5 4 3 2 1 0 TF2 EXF2 RCLK TCLK EXEN2 TR2 C/T2 CP/RL2 Bit Mnemonic 7 TF2 6 5 4 3 2 Capture/Reload Select. 1: Capture of Timer 2 value into RCAP2H, RCAP2L is performed if EXEN2=1 and a negative transitions occurs on the T2EX pin. The capture mode requires RCLK and TCLK to be 0. CP/RL2 EXF2 RCLK TCLK EXEN2 TR2 1 C/T2 Description Timer 2 Overflow Flag: Set by an overflow of Timer 2 and must be cleared by software. TF2 will not be set when either RCLK =1 or TCLK =1. Timer 2 external flag change in state occurs when either a capture or reload is caused by a negative transition on T2EX and EXEN2=1. When Timer 2 is enabled, EXF=1 will cause the CPU to Vector to the Timer 2 interrupt routine. Note that EXF2 must be cleared by software. Serial Port Receive Clock Source. 1: Causes Serial Port to use Timer 2 overflow pulses for its receive clock in modes 1 and 3. 0: Causes Timer 1 overflow to be used for the Serial Port receive clock. Serial Port Transmit Clock. 1: Causes Serial Port to use Timer 2 overflow pulses for its transmit clock in modes 1 and 3. 0: Causes Timer 1 overflow to be used for the Serial Port transmit clock. Timer 2 External Mode Enable. 1: Allows a capture or reload to occur as a result of a negative transition on T2EX if Timer 2 is not being used to clock the Serial Port. 0: Causes Timer 2 to ignore events at T2EX. Start/Stop Control for Timer 2. 1: Start Timer 2 0: Stop Timer 2 Timer or Counter Select (Timer 2) 1: External event counter falling edge triggered. 0: Internal Timer (OSC/12) 0: Auto-reload reloads will occur either with Timer 2 overflows or negative transitions at T2EX when EXEN2=1. When either RCK =1 or TCLK =1, this bit is ignored and the timer is forced to auto-reload on Timer 2 overflow. As shown below, there are different possible combinations of control bits that may be used for the mode selection of Timer 2. T ABLE 16: T IMER 2 MODE SELECTION BITS RCLK + TCLK CP/RL2 TR2 0 0 1 0 1 1 1 X 1 X X 0 MODE 16-bit AutoReload Mode 16-bit Capture Mode Baud Rate Generator Mode Off The details of each mode are described as follows. Capture Mode In Capture Mode the EXEN2 bit value defines if the external transition on the T2EX pin will be able to trigger the capture of the timer value. When EXEN2 = 0, Timer 2 acts as a 16-bit timer or counter, which, upon overflowing, will set bit TF2 (Timer 2 overflow bit). This overflow can be used to generate an interrupt. FIGURE 14: T IMER 2 IN CAPTURE MODE FOSC /12 0 TIMER 0 TL2 TH2 7 0 7 0 7 C/T2 1 COUNTER T2 Pin 0 RCAP2L RCAP2H 7 TR2 TF2 T2 EX Pin EXF2 EXEN2 Timer 2 Interrupt ______________________________________________________________________________________________ www.ramtron.com page 16 of 40 VRS51x540 When EXEN2 = 1, the above still applies. Additionally, it is possible to allow a 1 to 0 transition at the T2EX input to cause the current value stored in the Timer 2 registers (TL2 and TH2) to be captured by the RCAP2L and RCAP2H registers. Furthermore, the transition at T2EX causes bit EXF2 in T2CON to be set, and EXF2, like TF2, can generate an interrupt. Note that both EXF2 and TF2 share the same interrupt vector. FOSC /2 0 TIMER TL2 0 0 7 0 7 1 COUNTER T2 Pin 0 RCAP2L RCAP2H 7 TR2 1 0 0 Timer 1 Overflow /2 Auto-Reload Mode T2 EX Pin TCLK /16 TX Clock /16 RX Clock 1 0 1 SMOD In this mode, there are also two options. The user may choose either option by writing to bit EXEN2 in T2CON. TH2 7 C/T2 RCLK EXF2 Timer 2 Interrupt Request EXEN2 If EXEN2 = 0, when Timer 2 rolls over, it not only sets TF2, but also causes the Timer 2 registers to be reloaded with the 16-bit value in the RCAP2L and RCAP2H registers previously initialised. In this mode, Timer 2 can be used as a baud rate generator source for the serial port. If EXEN2=1, then Timer 2 still performs the above operation, but a 1 to 0 transition at the external T2EX input will also trigger an anticipated reload of the Timer 2 with the value stored in RCAP2L, RCAP2H and set EXF2. FIGURE 15: T IMER 2 IN AUTO-RELOAD MODE FOSC /12 0 TIMER 0 TL2 TH2 7 0 7 0 7 C/T2 1 COUNTER T2 Pin 0 RCAP2L RCAP2H 7 TR2 TF2 T2 EX Pin EXF2 EXEN2 Timer 2 Interrupt Baud Rate Generator Mode The baud rate generator mode is activated when RCLK is set to 1 and/or TCLK is set to 1. This mode will be described in the serial port section. FIGURE 16: T IMER 2 IN AUTOMATIC BAUD GENERATOR MODE ______________________________________________________________________________________________ www.ramtron.com page 17 of 40 VRS51x540 2 Serial Port The serial port included in the VRS51x540 can operate in full duplex; in other words, it can transmit and receive data simultaneously. This occurs at the same speed if one timer is assigned as the clock source for both transmission and reception, and at different speeds if transmission and reception are each controlled by their own timer. The serial port receive is buffered, which means that it can begin reception of a byte even if the one previously received byte has not been retrieved from the receive register by the processor. However, if the first byte still has not been read by the time reception of the second byte is complete, the byte present in the receive buffer will be lost. The SBUF register provides access to the transmit and receive registers of the serial port. Reading from the SBUF register will access the receive register, while a write to the SBUF loads the transmit register. 1 0 th RB8 9 data bit received in modes 2 and 3. TI In Mode 1, if SM2 = 0, RB8 is the stop bit that was received. In Mode 0, this bit is not used. This bit must be cleared by software. Transmission Interrupt flag. RI Automatically set to 1 when: th * The 8 bit has been sent in Mode 0. * Automatically set to 1 when the stop bit has been sent in the other modes. This bit must be cleared by software. Reception Interrupt flag Automatically set to 1 when: th * The 8 bit has been received in Mode 0. * Automatically set to 1 when the stop bit has been sent in the other modes (see SM2 exception). This bit must be cleared by software. T ABLE 18: SERIAL PORT MODES OF OPERATION SM0 SM1 Mode Description Baud Rate 0 0 1 0 1 0 0 1 2 Shift Register 8-bit UART 9-bit UART 1 1 3 9-bit UART Fosc/12 Variable Fosc/64 or Fosc/32 Variable Serial Port Control Register The SCON (serial port control) register contains control and status information, and includes the 9th data bit for transmit/receive (TB8/RB8 if required), mode selection bits and serial port interrupt bits (TI and RI). T ABLE 17: SERIAL PORT CONTROL REGISTER (SCON) - SFR 98H 7 6 5 4 3 2 1 0 SM0 SM1 SM2 REN TB8 RB8 TI RI Bit 7 Mnemonic SM0 6 SM1 5 SM2 Description Bit to select mode of operation (see table below) Bit to select mode of operation (see table below) Multiprocessor communication is possible in modes 2 and 3. Modes of Operation The VRS51x540 serial port can operate in four different modes. In all four modes, a transmission is initiated by an instruction that uses the SBUF SFR as a destination register. In Mode 0, reception is initiated by setting RI to 0 and REN to 1. An incoming start bit initiates reception in the other modes provided that REN is set to 1. The following paragraphs describe the four modes. In modes 2 or 3 if SM2 is set to 1, RI will th not be activated if the received 9 data bit (RB8) is 0. 4 REN 3 TB8 In Mode 1, if SM2 = 1 then RI will not be activated if a valid stop bit was not received. Serial Reception Enable Bit This bit must be set by software and cleared by software. 1: Serial reception enabled 0: Serial reception disabled th 9 data bit transmitted in modes 2 and 3 This bit must be set by software and cleared by software. ______________________________________________________________________________________________ www.ramtron.com page 18 of 40 VRS51x540 Mode 0 In this mode, the serial data exits and enters through the RXD pin. TXD is used to output the shift clock. The signal is composed of 8 data bits starting with the LSB. The baud rate in this mode is 1/12 the oscillator frequency. The SEND signal enables the output of the shift register to the alternate output function line of P3.0 and enables SHIFT CLOCK to the alternate output function line of P3.1. SHIFT CLOCK is high during T11, T12 and T1, T2 and T3, T4 of every machine cycle and low during T5, T6, T7, T8, T9 and T10. At T12 of every machine cycle in which SEND is active and the contents of the transmit shift register are shifted to the right by one position. Internal Bus 1 Write to SBUF Q S SBUF RXD P3.0 D Shift CLK ZERO DETECTOR Shift Clock TXD P3.1 Shift Start TX Control Unit TX Clock Fosc/12 Send TI Serial Port Interrupt RI RX Clock Receive Reception in Mode 0 RX Control Unit RI REN Start Shift 1 RXD P3.0 Input Function 1 1 1 1 1 1 Shift Register SBUF Zeros come in from the left as data bits shift out to the right. The TX control block sends its final shift and deactivates SEND while setting T1 after one condition is fulfilled: When the MSB of the data byte is at the output position of the shift register; the 1 that was initially loaded into the 9th position is just to the left of the MSB; and all positions to the left of that contain zeros. Once these conditions are met, the de-activation of SEND and the setting of T1 occur at T1 of the 10th machine cycle after the "write to SBUF" pulse. 0 RXD P3.0 READ SBUF Internal Bus FIGURE 17: SERIAL PORT MODE 0 BLOCK DIAGRAM Transmission in Mode 0 Any instruction that uses SBUF as a destination register may initiate a transmission. The "write to SBUF" signal also loads a 1 into the 9th position of the transmit shift register and tells the TX control block to begin a transmission. The internal timing is such that one full machine cycle will elapse between a write to SBUF instruction and the activation of SEND. When REN and R1 are set to 1 and 0 respectively, reception is initiated. The bits 11111110 are written to the receive shift register at T12 of the next machine cycle by the RX control unit. In the following phase, the RX control unit will activate RECEIVE. SHIFT CLOCK to the alternate output function line of P3.1 is enabled by RECEIVE. At every machine cycle, SHIFT CLOCK makes transitions at T5 and T11. The contents of the receive shift register are shifted one position to the left at T12 of every machine in which RECEIVE is active. The value that comes in from the right is the value that was sampled at the P3.0 pin at T10 of the same machine cycle. 1's are shifted out to the left as data bits are shifted in from the right. The RX control block is flagged to do one last shift and load SBUF when the 0 that was initially loaded into the rightmost position arrives at the leftmost position in the shift register. ______________________________________________________________________________________________ www.ramtron.com page 19 of 40 VRS51x540 Mode 1 For an operation in Mode 1, 10 bits are transmitted through TXD or received through RXD. The transactions are composed of: a Start bit (Low), 8 data bits (LSB first) and one Stop bit (high). The reception is completed once the Stop bit sets the RB8 flag in the SCON register. Either Timer 1 or Timer 2 controls the baud rate in this mode. The following diagram shows the serial port structure when configured in Mode 1. FIGURE 18: SERIAL PORT MODE 1 AND 3 BLOCK DIAGRAM Internal Bus When a transmission begins, it places the start bit at TXD. Data transmission is activated one bit time later. This activation enables the output bit of the transmit shift register to TXD. One bit time after that, the first shift pulse occurs. In this mode, zeros are clocked in from the left as data bits are shifted out to the right. When the most significant bit of the data byte is at the output position of the shift register, the 1 that was initially loaded into the 9th position is to the immediate left of the MSB, and all positions to the left of that contain zeros. This condition flags the TX Control Unit to shift one more time. Reception in Mode 1 1 Write to SBUF Timer 1 Overflow Q S SBUF TXD D CLK Timer 2 Overflow /2 ZERO DETECTOR 0 1 SMOD 0 Shift Start 1 /16 0 Data TX Control Unit TCLK TX Clock Send TI 1 RCLK /16 Serial Port Interrupt RX Clock 1-0 Transition Detector RXD Start RI Load SBUF RX Control Unit Bit Detector SHIFT 9-Bit Shift Register Shift LOAD SBUF SBUF READ SBUF One to zero transitions at RXD initiates reception. It is for this reason that RXD is sampled at a rate of 16 multiplied by the baud rate that has been established. When a transition is detected, 1FFh is written into the input shift register and the divide-by-16 counter is immediately reset. The divide-by-16 counter is reset in order to align its rollovers with the boundaries of the incoming bit times. In total, there are 16 states in the counter. During the 7th, 8th and 9th counter states of each bit time; the bit detector samples the value of RXD. The accepted value is the value that was seen in at least two of the three samples. The purpose of doing this is for noise rejection. If the value accepted during the first bit time is not zero, the receive circuits are reset and the unit goes back to searching for another one to zero transition. Doing this rejects all false start bits. If the start bit is valid, it is shifted into the input shift register, and the reception of the rest of the frame will proceed. Internal Bus Transmission in Mode 1 Transmission is initiated by any instruction that makes use of SBUF as a destination register. The 9th bit position of the transmit shift register is loaded by the "write to SBUF" signal. This event also flags the TX Control Unit that a transmission has been requested. It is after the next rollover in the divide-by-16 counter when transmission actually begins at T1 of the machine cycle. It follows that the bit times are synchronized to the divide-by-16 counter and not to the "write to SBUF" signal. For a receive operation, the data bits come in from the right as 1's shift out on the left. As soon as the start bit arrives at the leftmost position in the shift register, (9bit register), it tells the RX control block to perform one last shift operation: to set RI and to load SBUF and RB8. The signal to load SBUF and RB8, and to set RI, will be generated if, and only if, the following conditions are met at the time the final shift pulse is generated: - Either SM2 = 0 or the received stop bit = 1 RI = 0 ______________________________________________________________________________________________ www.ramtron.com page 20 of 40 VRS51x540 If both conditions are met, the stop bit goes into RB8, the 8 data bits go into SBUF, and RI is activated. If one of these conditions is not met, the received frame is completely lost. At this time, whether the above conditions are met or not, the unit goes back to searching for a one to zero transition in RXD. Mode 3 Mode 2 Mode 3 is identical to Mode 2 in all respects but one: the baud rate. Either Timer 1 or Timer 2 generates the baud rate in Mode 3. In Mode 3, 11-bits are transmitted through TXD or received through RXD. The transactions are composed of: a Start bit (Low), 8 data bits (LSB first), a programmable 9th data bit, and one Stop bit (High). In Mode 2 a total of 11-bits are transmitted through TXD or received through RXD. The transactions are composed of: a Start bit (Low), 8 data bits (LSB first), a programmable 9th data bit, and one Stop bit (High). FIGURE 20: SERIAL PORT MODE 3 BLOCK DIAGRAM Internal Bus 1 For transmission, the 9th data bit comes from the TB8 bit of SCON. For example, the parity bit P in the PSW could be moved into TB8. Write to SBUF Timer 1 Overflow Q S SBUF TXD D th CLK In the case of receive, the 9 data bit is automatically written into RB8 of the SCON register. Timer 2 Overflow /2 ZERO DETECTOR 0 1 SMOD In Mode 2, the baud rate is programmable to either 1/32 or 1/64 the oscillator frequency. 0 Start 1 Shift /16 0 Data TX Control Unit TCLK TX Clock Send TI 1 RCLK /16 Serial Port Interrupt FIGURE 19: SERIAL PORT MODE 2 BLOCK DIAGRAM SAMPLE RX Clock 1-0 Transition Detector Start RI Load SBUF RX Control Unit SHIFT Internal Bus 1 Write to SBUF RXD Bit Detector 9-Bit Shift Register Shift LOAD SBUF Q S Fosc/2 SBUF TXD D SBUF CLK READ SBUF ZERO DETECTOR /2 Internal Bus 0 1 Shift Stop Start SMOD /16 TX Clock Send TI /16 Sample 1-0 Transition Detector RXD Data TX Control Unit Serial Port Interrupt RX Clock Control Start Bit Detector RI Load SBUF RX Control Unit SHIFT 9-Bit Shift Register Shift LOAD SBUF SBUF READ SBUF Internal Bus ______________________________________________________________________________________________ www.ramtron.com page 21 of 40 VRS51x540 Mode 2 and 3: Additional Information Reception in Mode 2 and Mode 3 As mentioned earlier, for an operation in these modes, 11 bits are transmitted through TXD or received through RXD. The signal comprises: a logical low Start bit, 8 data bits (LSB first), a programmable 9th data bit and one logical high Stop bit. One to zero transitions at RXD initiate reception. It is for this reason that RXD is sampled at a rate of 16 multiplied by the baud rate that has been established. When a transition is detected, the 1FFh is written into the input shift register and the divide-by-16 counter is immediately reset. On transmit, (TB8 in SCON) can be assigned the value of 0 or 1. On receive; the 9th data bit goes into RB8 in SCON. The baud rate is programmable to either 1/32 or 1/64 with the oscillator frequency in Mode 2. Mode 3 may have a variable baud rate generated from either Timer 1 or Timer 2 depending on the states of TCLK and RCLK. Transmission in Mode 2 and Mode 3 The transmission is initiated by any instruction that makes use of SBUF as the destination register. The 9th bit position of the transmit shift register is loaded by the "write to SBUF" signal. This event also informs the TX control unit that a transmission has been requested. After the next rollover in the divide-by-16 counter, a transmission actually begins at T1 of the machine cycle. It follows the bit times that are synchronized to the divide-by-16 counter and not to the "write to SBUF" signal, as in the previous mode. Transmission begins when the SEND signal is activated, which places the Start bit at TXD. Data is activated one bit time later. This activation enables the output bit of the transmit shift register to TXD. The first shift pulse occurs one bit time after that. The first shift clocks a Stop bit (1) into the 9th bit position of the shift register to TXD. Thereafter, only zeros are clocked in. Thus, as data bits shift out to the right, zeros are clocked in from the left. When TB8 is at the output position of the shift register, the stop bit is just to the left of TB8, and all positions to the left of that contain zeros. This condition signals to the TX control unit to shift one more time and set TI, while deactivating SEND. This occurs at the 11th divide-by-16 rollover after "write to SBUF". During the 7th, 8th and 9th counter states of each bit time; the bit detector samples the value of RXD. The accepted value is the value that was seen in at least two of the three samples. If the value accepted during the first bit time is not zero, the receive circuits are reset and the unit goes back to searching for another one to zero transition. If the start bit is valid, it is shifted into the input shift register, and the reception of the rest of the frame will proceed. For a receive operation, the data bits come in from the right as 1's shift out on the left. As soon as the start bit arrives at the leftmost position in the shift register (9-bit register), it tells the RX control block to do one more shift, to set RI, and to load SBUF and RB8. The signal to set RI and to load SBUF and RB8 will be generated if, and only if, the following conditions are satisfied at the instance when the final shift pulse is generated: - Either SM2 = 0 or the received 9th bit is equal to 1 - RI = 0 If both conditions are met, the 9th data bit received goes into RB8, and the first 8 data bits go into SBUF. If one of these conditions is not met, the received frame is completely lost. One bit time later, whether the above conditions are met or not, the unit goes back to searching for a one to zero transition at the RXD input. Please note that the value of the received stop bit is unrelated to SBUF, RB8 or RI. ______________________________________________________________________________________________ www.ramtron.com page 22 of 40 VRS51x540 UART Baud Rate Calculation The value to write into the TH1 register is defined by the following formula: In Mode 0, the baud rate is fixed and can be represented by the following formula: TH1 = 256 Mode 0 Baud Rate = Oscillator Frequency 12 In Mode 2, the baud rate depends on the value of the SMOD bit in the PCON SFR. From the formula below, we can see that if SMOD = 0 (which is the value on reset), the baud rate is 1/32 the oscillator frequency. 2SMODx Fosc 32 x 12x (Baud Rate) It is possible to use Timer 1 in 16-bit mode to generate the baud rate for the serial port. To do this, leave the Timer 1 interrupt enabled, configure the timer to run as a 16-bit timer (high nibble of TMOD = 0001B), and use the Timer 1 interrupt to perform a 16-bit software reload. This can achieve very low baud rates. Generating Baud Rates with Timer 2 Mode 2 Baud Rate = 2SMOD x (Oscillator Frequency) 64 The Timer 1 and/or Timer 2 overflow rate determines the baud rates in modes 1 and 3. Timer 2 is often preferred to generate the baud rate, as it can be easily configured to operate as a 16-bit timer with auto-reload. This allows for much better resolution than using Timer 1 in 8-bit auto-reload mode. The baud rate using Timer 2 is defined as: Generating Baud Rates with Timer 1 When Timer 1 functions as a baud rate generator, the baud rate in modes 1 and 3 are determined by the Timer 1 overflow rate. SMOD Mode 1, 3 Baud Rate = 2 x Timer 1 Overflow Rate 32 Timer 1 must be configured as an 8-bit timer (TL1) with auto-reload with TH1 value when an overflow occurs (Mode 2). In this application, the Timer 1 interrupt should be disabled. The two following formulas can be used to calculate the baud rate and the reload value to written into the TH1 register. Mode 1, 3 Baud Rate = Mode 1, 3 Baud Rate = Timer 2 Overflow Rate 16 The timer can be configured as either a timer or a counter in any of its 3 running modes. In most applications, it is configured as a timer (C/T2 is set to 0). To make the Timer 2 operate as a baud rate generator the TCLK and RCLK bits of the T2CON register must be set to 1. The baud rate generator mode is similar to the autoreload mode in that an overflow in TH2 causes the Timer 2 registers to be reloaded with the 16-bit value in registers RCAP2H and RCAP2L, which are preset by software. However, when Timer 2 is configured as a baud rate generator, its clock source is Osc/2. SMOD 2 x Fosc 32 x 12(256 - TH1) ______________________________________________________________________________________________ www.ramtron.com page 23 of 40 VRS51x540 The following formula can be used to calculate the baud rate in modes 1 and 3 using the Timer 2: Modes 1, 3 Baud Rate = Oscillator Frequency 32x[65536 - (RCAP2H, RCAP2L)] The formula below is used to define the reload value to put into the RCAP2h, RCAP2L registers to achieve a given baud rate. (RCAP2H, RCAP2L) = 65536 - Fosc 32x[Baud Rate] In the above formula, RCAP2H and RCAP2L are the contents of RCAP2H and RCAP2L taken as a 16-bit unsigned integer. Note that a rollover in TH2 does not set TF2, and will not generate an interrupt and because of this, the Timer 2 interrupt does not have to be disabled when Timer 2 is configured in baud rate generator mode. Also, if EXEN2 is set, a 1-to-0 transition in T2EX will set EXF2 but will not cause a reload from RCAP2x to Tx2. Therefore, when Timer 2 is used as a baud rate generator, T2EX can be used as an extra external interrupt. Furthermore, when Timer 2 is running (TR2 is set to 1) as a timer in baud rate generator mode, the user should not try to read or write to TH2 or TL2. When operating under these conditions, the timer is being incremented every state time and the results of a read or write command may be inaccurate. The RCAP2 registers, however, may be read but should not be written to, because a write may overlap a reload operation and generate write and/or reload errors. In this case, before accessing the Timer 2 or RCAP2 registers, be sure to turn the timer off by clearing TR2. ______________________________________________________________________________________________ www.ramtron.com page 24 of 40 VRS51x540 Interrupts Interrupt Vectors The VRS51x540 has 8 interrupts and 7 interrupt vectors (including reset) used for handling. The table below specifies each interrupt source, its flag and its vector address. The interrupt can be enabled via the IE register shown below: T ABLE 20: INTERRUPT VECTOR CORRESPONDING FLAGS ANS VECTOR ADDRESS Interrupt Source Flag T ABLE 19: IEN0 INTERRUPT E NABLE REGISTER -SFR A8H 7 6 5 4 3 EA - ET2 ES ET1 Bit 7 Mnemonic EA 6 - 5 4 3 2 1 0 ET2 ES ET1 EX1 ET0 EX0 2 EX1 1 0 ET0 EX0 Description Disables All Interrupts 0: no interrupt acknowledgment 1: Each interrupt source is individually enabled or disabled by setting or clearing its enable bit. Reserved Timer 2 Interrupt Enable Bit Serial Port Interrupt Enable Bit Timer 1 Interrupt Enable Bit External Interrupt 1 Enable Bit Timer 0 Interrupt Enable Bit External Interrupt 0 Enable Bit The following figure illustrates the various interrupt sources on the VRS51x540. FIGURE 21: INTERRUPT SOURCES INT0 IT0 WDRESET IE0 TF0 IE1 TF1 RI+TI TF2+EXF2 External Interrupts The VRS51x540 has two external interrupt inputs named INT0 and INT1. These interrupt lines are shared with P3.2 and P3.3. The bits IT0 and IT1 of the TCON register determine whether the external interrupts are level or edge sensitive. If ITx = 1, the interrupt will be raised when a 1 to 0 transition occurs at the interrupt pin. For the interrupt to be noticed by the processor, the duration of the sum high and low condition must be at least equal to 12 oscillator cycles. IE0 If ITx = 0, the interrupt will occur when a logic low condition is present on the interrupt pin. TF0 INT1 RESET (+ WDT) INT0 Timer 0 INT1 Timer 1 Serial Port Timer 2 Vector Address 0000h 0003h 000Bh 0013h 001Bh 0023h 002Bh IT1 IE1 INTERRUPT SOURCES The state of the external interrupt, when enabled, can be monitored using the flags, IE0 and IE1 of the TCON register that are set when the interrupt condition occurs. TF1 T1 RI TF2 EXF2 In the case where the interrupt was configured as edge sensitive, the associated flag is automatically cleared when the interrupt is serviced. If the interrupt is configured as level sensitive, then the interrupt flag must be cleared by the software. ______________________________________________________________________________________________ www.ramtron.com page 25 of 40 VRS51x540 Timer 0 and Timer 1 Interrupt Execution of an Interrupt Both Timer 0 and Timer 1 can be configured to generate an interrupt when a rollover of the timer/counter occurs (except Timer 0 in Mode 3). When the processor receives an interrupt request, an automatic jump to the desired subroutine occurs. This jump is similar to executing a branch to a subroutine instruction: the processor automatically saves the address of the next instruction on the stack. An internal flag is set to indicate that an interrupt is taking place, and then the jump instruction is executed. An interrupt subroutine must always end with the RETI instruction. This instruction allows users to retrieve the return address placed on the stack. The TF0 and TF1 flags serve to monitor timer overflow occurring from Timer 0 and Timer 1. These interrupt flags are automatically cleared when the interrupt is serviced. Timer 2 Interrupt A Timer 2 interrupt can occur if TF2 and/or EXF2 flags are set to 1 and if the Timer 2 interrupt is enabled. The RETI instruction also allows updating of the internal flag that will take into account an interrupt with the same priority. The TF2 flag is set when a rollover of the Timer 2 Counter/Timer occurs. The EXF2 flag can be set by a 1 to 0 transition on the T2EX pin by the software. Interrupt Enable and Interrupt Priority Note that neither flag is cleared by the hardware upon execution of the interrupt service routine. The service routine may have to determine whether it was TF2 or EXF2 that generated the interrupt. These flag bits will have to be cleared by the software. When the VRS51x540 is initialized, all interrupt sources are inhibited by the bits of the IE register being reset to 0. It is necessary to start by enabling the interrupt sources that the application requires. This is achieved by setting bits in the IE register, as discussed previously. Every bit that generates interrupts can either be cleared or set by the software, yielding the same result as when the operation is done by the hardware. In other words, pending interrupts can be cancelled and interrupts can be generated by the software. This register is part of the bit addressable internal RAM. For this reason, it is possible to modify each bit individually in one instruction without having to modify the other bits of the register. All interrupts can be inhibited by setting EA to 0. Serial Port Interrupt The order in which interrupts are serviced is shown in the following table: The serial port can generate an interrupt upon byte reception or once the byte transmission is completed. Those two conditions share the same interrupt vector and it is up to the user developed interrupt service routine software to ascertain the cause of the interrupt by looking at the serial interrupt flags RI and TI. Note that neither of these flags is cleared by the hardware upon execution of the interrupt service routine. The software must clear these flags. T ABLE 21: INTERRUPT NATURAL PRIORITY Interrupt Source RESET + WDT (Highest Priority) IE0 TF0 IE1 TF1 RI+TI TF2+EXF2 (Lowest Priority) ______________________________________________________________________________________________ www.ramtron.com page 26 of 40 VRS51x540 Modifying the Interrupt Order of Priority The VRS51x540 allows the user to modify the natural priority of the interrupts by programming the bits in the IP (Interrupt Priority) register. When any bit in this register is set to 1, it gives the corresponding source a greater priority than interrupts coming from sources that don't have their corresponding IP bit set to 1. The IP register is represented in the table below. T ABLE 22: IP INTERRUPT PRIORITY REGISTER -SFR B8H 7 6 5 4 3 EA - ET2 ES ET1 2 EX1 1 0 ET0 EX0 Bit 7 6 Mnemonic - Description 5 4 3 2 1 0 PT2 PS PT1 PX1 PT0 PX0 Gives Timer 2 Interrupt Higher Priority Gives Serial Port Interrupt Higher Priority Gives Timer 1 Interrupt Higher Priority Gives INT1 Interrupt Higher Priority Gives Timer 0 Interrupt Higher Priority Gives INT0 Interrupt Higher Priority The user should check the WDRESET bit of the SYSCON register whenever an unpredicted reset has taken place. The WDT timeout delay can be adjusted by configuring the clock divider input for the time base source clock of the WDT. To select the divider value, bit2-bit0 (WDPS2~WDPS0) of the Watchdog Timer Control Register (WDTCON) should be set accordingly. Clearing the WDT is accomplished by setting the CLR bit of the WDTCON to 1. This action will clear the contents of the 16-bit counter and force it to restart. Watchdog Timer Registers Two registers of the VRS51x540 devices are associated with the Watchdog Timer: WDTCON and the SYSCON registers. The WDTCON register allows the user to enable the WDT, to clear the counter and to divide the clock source. The WDRESET bit of the SYSCON register indicates whether the Watchdog Timer has caused the device reset. T ABLE 23: WATCHDOG T IMER REGISTERS: WDTCON - SFR 9FH Watchdog Timer The Watchdog Timer (WDT) is a 16-bit free-running counter that generates a reset signal if the counter overflows. The WDT is useful for systems that are susceptible to noise, power glitches and other conditions that can cause the software to go into infinite dead loops or runaways. The WDT function gives the user software a recovery mechanism from abnormal software operation. 7 WDTE Bit 7 6 5 [4:3] 2 1 0 6 Unused 5 WDCLR 4 3 Unused 2 1 0 WDTPS [2:0] Mnemonic WDTE Unused WDCLR Unused Description Watchdog Timer Enable Bit Watchdog Timer Counter Clear Bit - WDPS [2:0] Watchdog Timer Clock Source Divider The Watchdog Timer of the VRS51x540 is driven by the device's oscillator. To enable the WDT, the user must set bit 7 (WDTE) of the WDTCON register to 1. Once WDTE has been set to 1, the 16-bit counter will start to count with the selected time base source clock configured in WDPS2~WDPS0. The Watchdog Timer will generate a reset signal if an overflow has taken place. The WDTE bit will be cleared to 0 automatically when the device is reset by either the hardware or a WDT reset. Once the WDT is enabled, the user software must clear it periodically. In the case where the WDT is not cleared, its overflow will trigger a reset of the device. ______________________________________________________________________________________________ www.ramtron.com page 27 of 40 VRS51x540 The table below shows example Watchdog timeout periods that the user will obtain for different values of the WDPSx bits of the Watchdog Timer Register. T ABLE 24: WATCHDOG T IMER PERIOD VS. WDWDPS [2:0] BIT Fosc Division factor WDT Timeout (ms) Fosc = 20MHz 000 8 26.2 001 16 52.4 010 011 32 64 104.8 209.7 100 128 419.4 101 256 110 512 1024 838.9 1677.7 WDPS [2:0] 111 XTAL C1 C2 R T ABLE 25: T HE SYSTEM CONTROL REGISTER (SYSCON)-SFR BFH 5 WDRESET Bit 7 [6:3] 2 1 0 Mnemonic WDRESET Unused Unused Unused ALEI 4 Unused 3 2 1 XRAME 3MHz 30 pF 30 pF open 6MHz 30 pF 30 pF open 12MHz 30 pF 30 pF open 16MHz 30 pF 30 pF open 25MHz 15 pF 15 pF 62KO Note: Oscillator circuits may differ with different crystals or ceramic resonators in higher oscillation frequency. 3355.4 The System Control register is used to monitor the status of the Watchdog Timer and inhibit the address Latch Enable signal output. 6 The crystal connected to the VRS51x540 oscillator input should be of a parallel type, operating in fundamental mode. The following table shows the value of capacitors and feedback resistor that must be used at different operating frequencies. The System Control Register 7 Crystal Consideration 0 ALEI Description Watchdog Timer Reset Status Bit - Crystals or ceramic resonator characteristics vary from one manufacturer to the other. The user should check the specific crystal or ceramic resonator technical literature available or contact the manufacturer to select the appropriate values for the external components. XTAL1 1: Enable Electromagnetic Interference Reducer 0: Disable Electromagnetic Interference Reducer The WDRESET bit of the SYSCON register is the Watchdog Timer Reset bit. It will be set to 1 when a reset signal is generated by the WDT overflow. The user should check the WDRESET bit state if a reset has taken place in application where the Watchdog timer is activated XTAL VRS51x540 R XTAL2 C1 C2 Reduced EMI Function The VRS51x540 can also be set up to reduce its EMI (electromagnetic interference) by setting bit 0 (ALEI) of the SYSCON register to 1. This function will inhibit the Fosc/6Hz clock signal output to the ALE pin. ______________________________________________________________________________________________ www.ramtron.com page 28 of 40 VRS51x540 Operating Conditions T ABLE 26: OPERATING CONDITIONS Symbol TA TS VCC5V VCC3V Fosc 25 Description Operating temperature Storage temperature Supply voltage Supply voltage Oscillator Frequency Min. -40 -55 4.5 3.0 3.0 Typ. 25 25 5.0 3.3 25 Max. 85 155 5.5 3.6 25 Unit C C V V MHz Remarks Ambient temperature operating 5 Volts devices 3.3 Volts devices For 5V & 3.3V application DC Characteristics T ABLE 27: DC CHARACTERISTICS AMBIENT T EMPERATURE = -40C TO 85C, 3.0V TO 5.5V Symbol VIL1 VIL2 VIH1 VI H2 VOL1 VOL2 Parameter Input Low Voltage Input Low Voltage Input High Voltage Input High Voltage Output Low Voltage Output Low Voltage Valid P o r t 0,1,2,3,4,#EA RES, XTAL1 P o r t 0,1,2,3,4,#EA RES, XTAL1 Port 0, ALE, #PSEN P o r t 1,2,3,4 VOH1 Output High Voltage Port 0 VOH2 Output High Voltage Port 1,2,3,4,ALE,#PSEN IIL Logical 0 Input Current ITL ILI R RES Logical Transition Current Input Leakage Current Reset Pull-down Resistance C -10 Pin Capacitance IC C Power Supply Current Max. 0.8 0.8 VCC+0.5 VCC+0.5 0.45 0.45 Unit V V V V V V V V V V Test Conditions P o r t 1,2,3,4 -75 uA Vin=0.45V P o r t 1,2,3,4 -650 uA Vin=2.OV P o r t 0, #EA +10 uA 0.45V<Vin<VCC 300 Kohm 10 pF Freq=1 MHz, Ta=25C 20 6.5 150 mA mA uA Active mode 12MHz Idle mode, 12MHz Power down mode RES Min. -0.5 0 2.0 70% VCC 2.4 90% VCC 2.4 90% VCC 50 VDD FIGURE 22: ICC IDLE MODE T EST CIRCUIT IOL=3.2mA IOL=1.6mA IOH=-800uA (Vcc = 5V) IOH=-80uA IOH=-60uA (Vcc = 5V) IOH=-10uA FIGURE 23: ICC ACTIVE MODE T EST CIRCUIT Vcc Vcc Vcc Icc RST VCC PO EA Icc VCC 8 RST VRS51x540 PO EA 8 VRS51x540 (NC) XTAL2 Clock Signal (NC) XTAL1 VSS Clock Signal XTAL2 XTAL1 VSS ______________________________________________________________________________________________ www.ramtron.com page 29 of 40 VRS51x540 AC Characteristics T ABLE 28: AC CHARACTERISTICS Symbol T LHLL T AVLL T LLAX T LLIV T LLPL T PLPH T PLIV T PXIX T PXIZ T AVI V T PLAZ T RLRH T WLWH T RLDV T RHDX T RHDZ T LLDV T AVDV T LLYL T AVYL T QVWH T QVWX T WHQX T RLAZ T YALH T CHCL T CLCX T CLCH T CHCX T , T C LCL Parameter ALE Pulse Width Address Valid to ALE Low Address Hold after ALE Low ALE Low to Valid Instruction In ALE Low to #PSEN low #PSEN Pulse Width #PSEN Low to Valid Instruction In Instruction Hold after #PSEN Instruction Float after #PSEN Address to Valid Instruction In #PSEN Low to Address Float #RD Pulse Width #WR Pulse Width #RD Low to Valid Data In Data Hold after #RD Data Float after #RD ALE Low to Valid Data In Address to Valid Data In ALE low to #WR High or #RD Low Address Valid to #WR or #RD Low Data Valid to #WR High Data Valid to #WR Transition Data Hold after #WR #RD Low to Address Float #W R or #RD High to ALE High Clock Fall Time Clock Low Time Clock Rise Time Clock High Time Clock Period Valid Cycle RD/WRT RD/WRT RD/WRT RD RD RD RD RD RD RD RD RD WRT RD RD RD RD RD RD/WRT RD/WRT WRT WRT WRT RD RD/WRT Fosc 16 Min. 115 43 53 Type Max. Variable Fosc Min. 2xT - 10 T - 20 T - 10 Type 240 53 173 4xT - 10 T - 10 3xT - 15 177 0 3xT -10 0 87 292 10 365 365 T + 25 5xT - 20 10 6xT - 10 6xT - 10 302 0 178 230 403 38 73 53 63 Max. 5xT - 10 0 145 590 542 197 72 2xT + 20 8xT - 10 9xT - 20 3xT + 10 3xT - 10 4xT - 20 7xT - 35 T - 25 T + 10 5 T+10 T -10 1/fosc Unit nS nS nS nS nS nS nS nS nS nS nS nS nS nS nS nS nS nS nS nS nS nS nS nS nS nS nS nS nS nS ______________________________________________________________________________________________ www.ramtron.com page 30 of 40 VRS51x540 Data Memory Read Cycle Timing The following timing diagram shows what occurs at each signal during a Data Memory Read Cycle. FIGURE 24: DATA MEMORY READ CYCLE T IMING T12 T1 T2 T3 T4 T5 T6 T7 T8 T9 T10 T11 T12 T1 T2 T3 OSC 1 ALE 2 #PSEN 5 #RD 7 3 ADDRESS A15-A8 PORT2 3 PORT0 INST in Float A7-A0 4 6 Float 8 Data in Float ADDRESS or Float ______________________________________________________________________________________________ www.ramtron.com page 31 of 40 VRS51x540 Program Memory Read Cycle Timing The following timing diagram shows what occurs at each signal during a Program Memory Read Cycle. FIGURE 25: PROGRAM MEMORY READ CYCLE T12 T1 T2 T3 T4 T5 T6 T7 T8 T9 T10 T11 T12 T1 T2 T3 OSC ALE 1 2 5 #PSEN 7 #RD,#WR 3 ADDRESS A15-A8 PORT2 PORT0 Float 3 4 6 A7-A0 Float INST in ADDRESS A15-A8 8 Float A7-A0 Float INST in Float ______________________________________________________________________________________________ www.ramtron.com page 32 of 40 VRS51x540 Data Memory Write Cycle Timing The following timing diagram shows what occurs at each signal during a Data Memory Write Cycle. FIGURE 26: DATA MEMORY WRITE CYCLE T IMING T12 T1 T2 T3 T4 T5 T6 T7 T8 T9 T10 T11 T12 T1 T2 T3 OSC ALE 1 #PSEN 5 #WR 6 2 ADDRESS A15-A8 PORT2 2 PORT0 INST in Float A7-A0 3 4 Data out ADDRESS or Float ______________________________________________________________________________________________ www.ramtron.com page 33 of 40 VRS51x540 I/O Port Timing The following timing diagram shows what occurs during I/O Port Timing. FIGURE 27: I/O PORTS T IMING T7 T8 T9 T10 T11 T12 T1 T2 T3 T4 T5 T6 T7 T8 X1 Sampled Inputs P0,P1 Sampled Inputs P2,P3 Output by Mov Px, Src RxD at Serial Port Shift Clock Mode 0 Current Data Next Data Sampled ______________________________________________________________________________________________ www.ramtron.com page 34 of 40 VRS51x540 External Clock Timing FIGURE 28: T IMING REQUIREMENT OF EXTERNAL CLOCK (VSS= 0.0V IS ASSUMED) TCLCL Vdd - 0.5V 0.45V 70% Vdd 20% Vdd-0.1V TCLCX TCHCX TCHCL TCLCH External Program Memory Read Cycle The following timing diagram shows what occurs at each signal during an External Program Memory Read Cycle. FIGURE 29: EXTERNAL PROGRAM MEMORY READ CYCLE TPLPH #PSEN TLLPL ALE TLHLL TPXIZ TAVLL PORT 0 TLLAX A0-A7 TPLIV TPLAZ TPXIX Instruction IN A0-A7 TAVIV PORT2 P2.0-P2.7 or AB-A15 from DPH A8-A15 ______________________________________________________________________________________________ www.ramtron.com page 35 of 40 VRS51x540 External Data Memory Read Cycle The following timing diagram shows what occurs at each signal during an External Data Memory Read Cycle. FIGURE 30: EXTERNAL DATA MEMORY READ CYCLE #PSEN TYHLH ALE TLLDV TRLRH TLLYL #RD TAVLL PORT 0 TRLDV TLLAX TRLAZ A0-A7 From Ri or DPL TRHDZ TRHDX DATA IN A0-A7 From PCL INSTRL IN TAVYL TAVDV PORT 2 P2.0-P2.7 or A8 -A15 from DPH A8-A15 from PCH ______________________________________________________________________________________________ www.ramtron.com page 36 of 40 VRS51x540 External Data Memory Write Cycle The following timing diagram shows what occurs at each signal during an External Data Memory Write Cycle. FIGURE 31: EXTERNAL DATA MEMORY WRITE CYCLE #PSEN TYHLH ALE TLHLL TLLYL TWLWH #WR TAVLL TQVWX TWHQX TLLAX TQVWH PORT 0 A0-A7 From Ri or DPL DATA OUT A0-A7 From PCL INSTRL IN TAVYL PORT 2 P2.0-P2.7 or A8-A15 from DPH A8-A15 from PCH . ______________________________________________________________________________________________ www.ramtron.com page 37 of 40 VRS51x540 Plastic Chip Carrier (PLCC-44) L VRS51x540 PLCC-44 GE E HE Y A2 D A1 A HD TABLE 29: DIMENSIONS OF PLCC-44 CHIP CARRIER C e b1 b GD Note: 1. Dimensions D & E do not include interlead Flash. 2. Dimension B1 does not include dambar protrusion/intrusion. 3. Controlling dimension: Inch 4. General appearance spec should be based on final visual inspection spec. Symbol A Al A2 bl b C D E e GD GE HD HE L ? ?y Dimension in inch Minimal/Maximal -/0.185 0.020/0.145/0.155 0.026/0.032 0.016/0.022 0.008/0.014 0.648/0.658 0.648/0.658 0.050 BSC 0.590/0.630 0.590/0.630 0.680/0.700 0.680/0.700 0.090/0.110 -/0.004 / Dimension in mm Minimal/Maximal -/4.70 0.51/ 3.68/3.94 0.66/0.81 0.41/0.56 0.20/0.36 16.46/16.71 16.46/16.71 1.27 BSC 14.99/16.00 14.99/16.00 17.27/17.78 17.27/17.78 2.29/2.79 -/0.10 / ______________________________________________________________________________________________ www.ramtron.com page 38 of 40 VRS51x540 C Quad Flat Package (QFP) L L1 S S VRS51x540 QFP-44 D2 D1 D b 2 R1 A2 A1 Gage Plane 0.25mm A 3 R2 E2 E1 E T ABLE 30: DIMENSIONS OF QFP-44 CHIP CARRIER Symbol e1 Seating Plane e Note: 1. Dimensions D1 and E1 do not include mold protrusion. 2. Allowance protrusion is 0.25mm per side. 3. Dimensions D1 and E1 do not include mold mismatch and are determined datum plane. 4. Dimension b does not include dambar protrusion. 5. Allowance dambar protrusion shall be 0.08 mm total in excess of the b dimension at maximum material condition. Dambar cannot be located on the lower radius of the lead foot. C A Al A2 b c D D1 D2 E E1 E2 e L L1 R1 R2 S 0 ?1 ?2 ?3 ?C Dimension in in. Minimal/Maximal -/0.100 0.006/0.014 0.071 / 0.087 0.012/0.018 0.004 / 0.009 0.520 BSC 0.394 BSC 0.315 0.520 BSC 0.394 BSC 0.315 0.031 BSC 0.029 / 0.041 0.063 0.005/0.005/0.012 0.008/0/7 0/ 10 REF 7 REF 0.004 Dimension in mm Minimal/Maximal -/2.55 0.15/0.35 1.80/2.20 0.30/0.45 0.09/0.20 13.20 BSC 10.00 BSC 8.00 13.20 BSC 10.00 BSC 8.00 0.80 BSC 0.73/1.03 1.60 0.13/0.13/0.30 0.20/as left as left as left as left 0.10 ______________________________________________________________________________________________ www.ramtron.com page 39 of 40 VRS51x540 Ordering Information Device Number Structure VRS51x540 Ordering Options Device Number VRS51C540-40-L VRS51L540-25-L VRS51C540-40-Q VRS51L540-25-Q VRS51C540-40-P VRS51L540-25-P VRS51C540-40-LG VRS51L540-25-LG VRS51C540-40-QG VRS51L540-25-QG VRS51C540-40-PG VRS51L540-25-PG Flash Size RAM Size 4KB 4KB 4KB 4KB 4KB 4KB 4KB 4KB 4KB 4KB 4KB 4KB 128 Bytes 128 Bytes 128 Bytes 128 Bytes 128 Bytes 128 Bytes 128 Bytes 128 Bytes 128 Bytes 128 Bytes 128 Bytes 128 Bytes Package Option PLCC-44 PLCC-44 QFP-44 QFP-44 DIP-40 DIP-40 PLCC-44 PLCC-44 QFP-44 QFP-44 DIP-40 DIP-40 Voltage Temperature Frequency 4.5V to 5.5V 3.0V to 3.6V 4.5V to 5.5V 3.0V to 3.6V 4.5V to 5.5V 3.0V to 3.6V 4.5V to 5.5V 3.0V to 3.6V 4.5V to 5.5V 3.0V to 3.6V 4.5V to 5.5V 3.0V to 3.6V -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C 40MHz 25MHz 40MHz 25MHz 40MHz 25MHz 40MHz 25MHz 40MHz 25MHz 40MHz 25MHz Disclaimers Right to make change - Ramtron reserves the right to make changes to its products - including circuitry, software and services - without notice at any time. Customers should obtain the most current and relevant information before placing orders. Use in applications - Ramtron assumes no responsibility or liability for the use of any of its products, and conveys no license or title under any patent, copyright or mask work right to these products and makes no representations or warranties that these products are free from patent, copyright or mask work right infringement unless otherwise specified. Customers are responsible for product design and applications using Ramtron parts. Ramtron assumes no liability for applications assistance or customer product design. Life support - Ramtron products are not designed for use in life support systems or devices. Ramtron customers using or selling Ramtron products for use in such applications do so at their own risk and agree to fully indemnify Ramtron for any damages resulting from such applications. ______________________________________________________________________________________________ www.ramtron.com page 40 of 40