Rev. 4257C–8051–01/04
Active Errata List
•During UART Recept ion, Clearing REN May Generate Unexpected IT
•Timer 2 – Baud Rate Generat or – Long S tart T ime
•C51 Core – Bad Exit of Power-dow n in X2 Mode
•PCA – Incorr ect Behavior with CPU X2 Mode Bit of HSB
•Timer0/1 – Extra Int errupt
Errata History
Er rata Descriptions
1. During UART Reception, Clearing REN May Generate Unexpected IT
Dur ing UART receptio n, if the REN b it is clea red betwe en sta rt bit de tectio n and
the end of recept ion, the UART will not discard the data (RI is set).
Workaround
Test REN at the begi nnin g of Int errupt ro uti ne di rectly after CLR RI , and ru n th e
Interrupt routine code only if REN is s et.
2. Timer 2 – Baud Rate Generator – Long S ta rt Time
When Ti mer 2 is used as a baud rate ge nerator, T H2 i s not lo aded with RCAP 2H
at the beginning, then UART is n ot operation al before 10,000 machine cycles.
Workaround
Add the initialization of TH2 and TL2 in the ini tialization of Timer 2.
3. C51 Core – Bad Exit of Power - d ow n in X2 Mode
When exiting power-down mode by interrupt while CPU is in X2 m ode, it lea ds t o
bad execution of the first instruction run when CPU restarts.
Workaround
Set the CPU in X 1 mode diretly before entering power-down mode.
4. PCA – Inco rrect behavi or with CPU X2 mode bit of HSB
When starting the microcontroller in X2 mode upon reset with the X2 fuse bit of
the HSB, the PCA may not work properly when configured with Timer 0 in X1
mode as clock input.
Workaround
Set the CPU in X2 mo de by s oftw are b y w rit ing C KC ON re gist er at the be gin of
the appli cation.
5. Timer0/1 – Extra Interrupt
When Tim er0 i s in X1 m ode an d Tim er1 in X2 mo de an d vi ce v ersa, ex tra inter-
rupt may randomly occur f o r Timer0 or Timer1.
Workaround
Use the same mode for the two t imers.
.
Lot Number Errata Li st
All 1, 2, 3, 4, 5 80C51 MCUs
AT89C51RD2
AT89C51ED2
Errata Sheet
24257C–8051–01/04
Active UART Bootloader Errata List
•API program Data Byte - Incorrect Return Value
•API program Data Page - In correct Return Value
UART Bootloader Errata History
UART Bootlo ader Errata Description
1. API program Data Byte - Incorrect Return V a lue
The PROGRAM DATA BYTE API returns t he ‘0xXX’ instead of 0x00 in ACC, but the programmnig operation is sucess-
fully completed.
2. API program Data Page- Incorrect Return Value
The PROGRAM DATA PAGE API returns the ‘0xXX’ inst ead of 0x00 in ACC, but the programmnig operation is sucess-
fully completed.
V ersion Number Errata Li st
0.0 (1. 0.0 di splayed by FLIP) 1,2
Pr inted o n rec ycled paper.
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