8Mb: 512K x16 Async/Page CellularRAM 1.0 Memory Features Async/Page CellularRAM(R) 1.0 Memory MT45W512KW16PEGA Features Figure 1: * Asynchronous and page mode interface * Random access time: 70ns * VCC, VCCQ voltages - 1.7-1.95V VCC - 1.7-3.6V1 VCCQ * Page mode read access - 16-word page size - Interpage read access: 70ns - Intrapage read access: 20ns * Low power consumption - Asynchronous READ: <20mA - Intrapage READ: <15mA - Standby: <65A - Deep power-down (DPD): <10A (TYP at 25C) * Low-power features - Partial-array refresh (PAR) - DPD mode Options Designator * Configuration - 512K x16 * Package - 48-ball VFBGA (green) * Access time - 70ns * Operating temperature range - Wireless (-30C to +85C)1 - Industrial (-40C to +85C) * Power options - Standby MT45W512KW16PE 48-Ball VFBGA Ball Assignments 1 2 3 4 5 6 A LB# OE# A0 A1 A2 ZZ# B DQ8 UB# A3 A4 CE# DQ0 C DQ9 DQ10 A5 A6 DQ1 DQ2 D VssQ DQ11 A17 A7 DQ3 Vcc E VccQ DQ12 NC A16 DQ4 Vss F DQ14 DQ13 A14 A15 DQ5 DQ6 G DQ15 NC A12 A13 WE# DQ7 H A18 A8 A9 A10 A11 NC Top view (Ball down) GA Part Number Example: -70 MT45W512KW16PEGA-70WT WT IT Blank Notes: 1. The 3.6V I/O and -30C wireless temperature exceed the CellularRAM Workgroup 1.0 specification. PDF: 09005aef82f264f6 / Source: 09005aef82f264aa 8mb_4mb_asyncpage_cr1_0_p22z__1.fm - Rev. C 4/08 EN 1 Micron Technology, Inc., reserves the right to change products or specifications without notice. (c)2007 Micron Technology, Inc. All rights reserved. Products and specifications discussed herein are subject to change by Micron without notice. 8Mb: 512K x16 Async/Page CellularRAM 1.0 Memory Table of Contents Table of Contents Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1 Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1 Table of Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2 List of Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3 List of Tables. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4 General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5 Functional Block Diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5 Ball Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6 Bus Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7 Part Numbering Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8 Valid Part Number Combinations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8 Device Marking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9 Power-Up Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9 Bus Operating Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9 Asynchronous Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9 Page Mode READ Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11 LB#/UB# Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11 Low-Power Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12 Standby Mode Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12 Partial-Array Refresh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12 Deep Power-Down Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13 Configuration Register Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14 Access Using ZZ# . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14 Software Access to the Configuration Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15 Electrical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17 Maximum and Typical Standby Currents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19 Timing Diagrams. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23 Package Dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27 Revision History. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28 PDF: 09005aef82f264f6 / Source: 09005aef82f264aa 4mb_asyncpage_cr1_0_p22zTOC.fm - Rev. C 4/08 EN 2 Micron Technology, Inc., reserves the right to change products or specifications without notice. (c)2007 Micron Technology, Inc. All rights reserved. 8Mb: 512K x16 Async/Page CellularRAM 1.0 Memory List of Figures List of Figures Figure 1: Figure 2: Figure 3: Figure 4: Figure 5: Figure 6: Figure 7: Figure 8: Figure 9: Figure 10: Figure 11: Figure 12: Figure 13: Figure 14: Figure 15: Figure 16: Figure 17: Figure 18: Figure 19: Figure 20: Figure 21: Figure 22: Figure 23: Figure 24: 48-Ball VFBGA Ball Assignments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1 Functional Block Diagram - 256K x 16 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5 Part Number Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8 Power-Up Initialization Timing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9 READ Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10 WRITE Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10 Page Mode READ Operation (ADV = LOW). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11 Software Access PAR Functionality. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13 Configuration Register Bit Mapping. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14 Load Configuration Register Operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14 Load Configuration Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15 Read Configuration Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16 Typical Refresh Current vs. Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19 AC Input/Output Reference Waveform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20 Output Load Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20 Power-Up Initialization Period . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23 Load Configuration Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23 Deep Power-Down Entry and Exit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23 Single READ Operation (WE# = VIH). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24 Page Mode READ Operation (WE# = VIH) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24 WRITE Cycle (WE# Control) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25 WRITE Cycle (CE# Control) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25 WRITE Cycle (LB#/UB# Control). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26 48-Ball VFBGA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27 PDF: 09005aef82f264f6 / Source: 09005aef82f264aa 4mb_asyncpage_cr1_0_p22zLOF.fm - Rev. C 4/08 EN 3 Micron Technology, Inc., reserves the right to change products or specifications without notice. (c)2007 Micron Technology, Inc. All rights reserved. 8Mb: 512K x16 Async/Page CellularRAM 1.0 Memory List of Tables List of Tables Table 1: Table 2: Table 3: Table 4: Table 5: Table 6: Table 7: Table 8: Table 9: Table 10: Table 11: VFBGA Ball Descriptions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6 Bus Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7 Absolute Maximum Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17 Electrical Characteristics and Operating Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18 Deep Power-Down Specifications and Conditions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20 Capacitance Specifications and Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20 READ Cycle Timing Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21 WRITE Cycle Timing Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22 Load Configuration Register Timing Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22 Deep Power-Down Timing Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22 Initialization Timing Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23 PDF: 09005aef82f264f6 / Source: 09005aef82f264aa 4mb_asyncpage_cr1_0_p22zLOT.fm - Rev. C 4/08 EN 4 Micron Technology, Inc., reserves the right to change products or specifications without notice. (c)2007 Micron Technology, Inc. All rights reserved. 8Mb: 512K x16 Async/Page CellularRAM 1.0 Memory General Description General Description Micron(R) CellularRAM(R) products are high-speed, CMOS memories developed for lowpower, portable applications. The MT45W512KW16PE is an 8Mb DRAM core device organized as 512K x 16 bits. These devices include the industry-standard, asynchronous memory interface found on other low-power SRAM or pseudo-SRAM (PSRAM) offerings. For seamless operation on an asynchronous memory bus, CellularRAM products incorporate a transparent self refresh mechanism. The hidden refresh requires no additional support from the system memory controller and has no significant impact on device read/write performance. A user-accessible configuration register (CR) defines how the CellularRAM device performs on-chip refresh and whether page mode read accesses are permitted. This register is loaded automatically with a default setting during power-up and can be updated at any time during normal operation. Special attention has been focused on current consumption during self refresh. This product includes two system-accessible mechanisms to minimize refresh current. Setting sleep enable (ZZ#) to LOW enables one of two low-power modes: partial-array refresh (PAR) or deep power-down (DPD). PAR limits refresh to only that part of the DRAM array that contains essential data. DPD halts refresh operation altogether and is used when no vital information is stored in the device. The system-configurable refresh mechanisms are accessed through the CR. Functional Block Diagram Figure 2: Functional Block Diagram - 512K x 16 A[18:0] Address decode logic 512K x 16 DRAM memory array Configuration register (CR) Input/ output MUX and buffers DQ[7:0] DQ[15:8] CE# WE# Control logic OE# UB# LB# ZZ# Notes: 1. Functional block diagrams illustrate simplified device operation. See the ball description table, bus operations table, and timing diagrams for detailed information. PDF: 09005aef82f264f6 / Source: 09005aef82f264aa 8mb_4mb_asyncpage_cr1_0_p22z__2.fm - Rev. C 4/08 EN 5 Micron Technology, Inc., reserves the right to change products or specifications without notice. (c)2007 Micron Technology, Inc. All rights reserved. 8Mb: 512K x16 Async/Page CellularRAM 1.0 Memory Ball Descriptions Ball Descriptions Table 1: VFBGA Ball Descriptions VFBGA Ball Assignment Symbol Type Description H1, D3, E4, F4, F3, G4, G3, H5, H4, H3, H2, D4, C4, C3, B4, B3, A5, A4, A3 B5 A[18:0] Input Address inputs: Inputs for the address accessed during READ or WRITE operations. The address lines are also used to define the value to be loaded into the CR. CE# Input A1 A2 LB# OE# Input Input B2 G5 A6 UB# WE# ZZ# Input Input Input Chip enable: Activates the device when LOW. When CE# is HIGH, the device is disabled and goes into standby power mode. Lower byte enable: DQ[7:0]. Output enable: Enables the output buffers when LOW. When OE# is HIGH, the output buffers are disabled. Upper byte enable: DQ[15:8]. Write enable: Enables WRITE operations when LOW. Sleep enable: When ZZ# is LOW, the CR can be loaded, or the device can enter one of two low-power modes (DPD or PAR). Data inputs/outputs. DQ[15:0] G1, F1, F2, E2, D2, C2, C1, B1, G6, F6, F5, E5, D5, C6, C5, B6 D6 VCC E1 E6 D1 E3, G2, H6 VCCQ VSS VSSQ NC PDF: 09005aef82f264f6 / Source: 09005aef82f264aa 8mb_4mb_asyncpage_cr1_0_p22z__2.fm - Rev. C 4/08 EN Input/ Output Supply Supply Supply Supply - VCC: Device power supply (1.7-1.95V). Power supply for device core operation. VCCQ: I/O power supply (1.7-3.6V). Power supply for input/output buffers. VSS: Must be connected to ground. VSSQ: Must be connected to ground. No connect: Not internally connected. 6 Micron Technology, Inc., reserves the right to change products or specifications without notice. (c)2007 Micron Technology, Inc. All rights reserved. 8Mb: 512K x16 Async/Page CellularRAM 1.0 Memory Bus Operations Bus Operations Table 2: Bus Operations Mode Standby Read Write No operation PAR DPD Load configuration register Notes: Power CE# WE# OE# LB#/UB# ZZ# DQ[15:0]1 Notes Standby Active Active Idle Partial-array refresh Deep power-down Active H L L L H H L X H L X X X L X L X X X X X X L L X X X X H H H H L L L High-Z Data-out Data-in X High-Z High-Z High-Z 2, 5 1, 4 1, 3, 4 4, 5 6 6 1. When LB# and UB# are in select mode (LOW), DQ[15:0] are affected. When LB# alone is in select mode, only DQ[7:0] are affected. When UB# alone is in the select mode, only DQ[15:8] are affected. 2. When the device is in standby mode, control inputs (WE#, OE#), address inputs, and data inputs/outputs are internally isolated from any external influence. 3. When WE# is active, the OE# input is internally disabled and has no effect on the I/Os. 4. The device will consume active power in this mode whenever addresses are changed. 5. VIN = VCCQ or 0V; all device balls must be static (unswitched) to achieve minimum standby current. 6. DPD is enabled when configuration register bit CR[4] is "0"; otherwise, PAR is enabled. PDF: 09005aef82f264f6 / Source: 09005aef82f264aa 8mb_4mb_asyncpage_cr1_0_p22z__2.fm - Rev. C 4/08 EN 7 Micron Technology, Inc., reserves the right to change products or specifications without notice. (c)2007 Micron Technology, Inc. All rights reserved. 8Mb: 512K x16 Async/Page CellularRAM 1.0 Memory Part Numbering Information Part Numbering Information Micron CellularRAM devices are available in several configurations and densities (see Figure 3). Figure 3: Part Number Chart MT 45 W 512K W 16 PE GA -70 WT ES Production Status Micron Technology Blank = Production Product Family ES = Engineering sample 45 = PSRAM/CellularRAM memory MS = Mechanical sample Operating Core Voltage Operating Temperature W = 1.7-1.95V WT = -30C to +85C (see Note 1) IT = -40C to +85C Address Locations Standby Power Options K = Kilobits Blank = Standard Operating Voltage W = 1.7-3.6V1 Access/cycle time 70 = 70ns Bus Configuration 16 = x16 READ/WRITE Operation Mode PE = Asynchronous/page Package Codes GA = 48-ball VFBGA "green" (6 x 8 grid, 0.75mm pitch, 6.0mm x 8.0mm x 1.0mm) Notes: 1. The 3.6V I/O and -30C exceed the CellularRAM Workgroup 1.0 specification. Valid Part Number Combinations After building the part number using the part numbering chart, visit the Micron Web site at www.micron.com/psram to verify that the part number is offered and valid. If the device required is not on this list, contact the factory. Device Marking Due to the size of the package, the Micron-standard part number is not printed on the top of the device. Instead, an abbreviated device mark consisting of a five-digit alphanumeric code is used. The abbreviated device marks are cross-referenced to the Micron part numbers at the FBGA Part Marking Decoder site: www.micron.com/decoder. To view the location of the abbreviated mark on the device, refer to customer service note CSN-11, "Product Mark/Label," at www.micron.com/csn. PDF: 09005aef82f264f6 / Source: 09005aef82f264aa 8mb_4mb_asyncpage_cr1_0_p22z__2.fm - Rev. C 4/08 EN 8 Micron Technology, Inc., reserves the right to change products or specifications without notice. (c)2007 Micron Technology, Inc. All rights reserved. 8Mb: 512K x16 Async/Page CellularRAM 1.0 Memory Functional Description Functional Description In general, the MT45W512KW16PEGA devices are high-density alternatives to SRAM and PSRAM products, which are popular in low-power, portable applications. MT45W512KW16PEGA devices contain an 8,388,608-bit DRAM core organized as 524,288 addresses by 16 bits. These devices include the industry-standard, asynchronous memory interface found on other low-power SRAM or PSRAM offerings. Page mode accesses are also included as a bandwidth-enhancing extension to the asynchronous read protocol. Power-Up Initialization CellularRAM products include an on-chip voltage sensor that is used to launch the power-up initialization process. Initialization will load the CR with its default setting. VCC and VCCQ must be applied simultaneously, and when they reach a stable level above 1.7V, the device will require 150s to complete its self-initialization process (see Figure 4). During the initialization period, CE# should remain HIGH. When initialization is complete, the device is ready for normal operation. Figure 4: Power-Up Initialization Timing Vcc (MIN) Vcc, VccQ = 1.7V tPU Device ready for normal operation Bus Operating Modes The MT45W512KW16PEGA CellularRAM product incorporates the industry-standard, asynchronous interface. This bus interface supports asynchronous READ and WRITE operations as well as page mode READ operation for enhanced bandwidth. The supported interface is defined by the value loaded into the CR. Asynchronous Mode CellularRAM products power up in the asynchronous operating mode. This mode uses the industry-standard SRAM control interface (CE#, OE#, WE#, and LB#/UB#). READ operations (Figure 5 on page 10) are initiated by bringing CE#, OE#, and LB#/UB# LOW while keeping WE# HIGH. Valid data will be driven out of the I/Os after the specified access time has elapsed. WRITE operations (Figure 6 on page 10) occur when CE#, WE#, and LB#/UB# are driven LOW. During WRITE operations, the level of OE# is a "Don't Care"; WE# will override OE#. The data to be written will be latched on the rising edge of CE#, WE#, or LB#/UB#, whichever occurs first. WE# LOW time must be limited to tCEM. PDF: 09005aef82f264f6 / Source: 09005aef82f264aa 8mb_4mb_asyncpage_cr1_0_p22z__2.fm - Rev. C 4/08 EN 9 Micron Technology, Inc., reserves the right to change products or specifications without notice. (c)2007 Micron Technology, Inc. All rights reserved. 8Mb: 512K x16 Async/Page CellularRAM 1.0 Memory Bus Operating Modes Figure 5: READ Operation CE# OE# WE# Address Data Valid address Valid data LB#/UB# tRC = READ cycle time Don't Care Figure 6: WRITE Operation CE# OE# < tCEM WE# Address Valid address Data Valid data LB#/UB# tWC = WRITE cycle time Don't Care PDF: 09005aef82f264f6 / Source: 09005aef82f264aa 8mb_4mb_asyncpage_cr1_0_p22z__2.fm - Rev. C 4/08 EN 10 Micron Technology, Inc., reserves the right to change products or specifications without notice. (c)2007 Micron Technology, Inc. All rights reserved. 8Mb: 512K x16 Async/Page CellularRAM 1.0 Memory Bus Operating Modes Page Mode READ Operation Page mode is a performance-enhancing extension to the legacy asynchronous READ operation. In page-mode-capable products, an initial asynchronous read access is performed, then adjacent addresses can be read quickly by simply changing the loworder address. Addresses A[3:0] are used to determine the members of the 16-address CellularRAM page. Any change in addresses A[4] or higher will initiate a new tAA access (see Figure 7). Page mode takes advantage of the fact that adjacent addresses can be read faster than random addresses. WRITE operations do not include comparable page mode functionality. The CE# LOW time is limited by refresh considerations. CE# must not stay LOW longer than tCEM. Figure 7: Page Mode READ Operation (ADV = LOW)