I have implemented a new serial data transfer protocol in our 8051 system (80C552). I tryed to write the received characters immediately back to the terminal with the following commands:
ucrs232_buffer[ucrec_count] = S0BUF; S0BUF = ucrs232_buffer[ucrec_count];
If you use my UART driver (see links at bottom of my page at http://www.embeddedfw.com) you can insert some test code in the main() function defined in uart.c. If my memory serves me correctly the good ol' 80C552 UART0 is located at the same place as the standard 8051's only UART - thus you shouldn't need to change any of my r_ variable addresses. Hope this helps. - Mark
you wrote:"Writing the chars back to S0BUF was just inserted for test. If I do not use this line, I get also a wrong message" If this is a fact, then writing back is not your problem, you must be writing to the buffer somewhere else. Erik also when writing, you must cleat TI in the ISR.