Active Errata List During UART Reception, Clearing REN May Generate Unexpected IT Timer 2 Baud Rate Generator Long Start Time Stretch MOVX Does Not Work Timer0/1 Extra Interrupt Errata History Lot Number Errata List 80C51 MCUs All 1, 2, 3, 4 Errata Descriptions AT89C51RB2 1. During UART Reception, Clearing REN May Generate Unexpected IT AT89C51RC2 During UART reception, if the REN bit is cleared between start bit detection and the end of reception, the UART will not discard the data (RI is set). Workaround Test REN at the beginning of Interrupt routine just after CLR RI, and run the Inter- Errata Sheet rupt routine code only if REN is set. 2. Timer 2 Baud Rate Generator Long Start Time When Timer 2 is used as a baud rate generator, TH2 is not loaded with RCAP2H at the beginning, then UART is not operational before 10,000 machine cycles. Workaround Add the initialization of TH2 and TL2 in the initialization of Timer 2. 3. Stretch MOVX Does Not Work When setting M0 bit in AUXR SFR (08Eh), the RD or WR pulse on a MOVX instruction on external memory is not 30 XTAL length but always standard 6 XTAL length. Thus slow external peripherals mapping in the XDATA space could not work properly. Workaround None. 4. Timer0/1 Extra Interrupt When Timer0 is in X1 mode and Timer1 in X2 mode and vice versa, extra inter- rupt may randomly occur for Timer0 or Timer1. Workaround Use the same mode for the two timers Rev. 4181C805106/04Active UART Bootloader Errata List API program Data Byte - Incorrect Return Value API program Data Page - Incorrect Return Value UART Bootloader Errata History Version Number Errata List 0.1 (1.0.1 displayed by FLIP) 1,2 UART Bootloader Errata Description 1. API program Data Byte - Incorrect Return Value The PROGRAM DATA BYTE API returns the 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 instead of 0x00 in ACC, but the programmnig operation is sucess- fully completed. 2 4181C805106/04