I am using a Atmel AT89C51 and I am having trouble doing serial communication. Here is what I am trying: #include <AT89X51.H> #include <STDIO.H> #include <intrins.h> int i,j; void main() { PCON |= 0x00; /* don't double baud rate */ SCON = 0x50; /* SCON: mode 1, 8-bit UART, enable rcvr */ TMOD |= 0x20; /* TMOD: timer 1, mode 2, 8-bit reload */ TH1 = 253; /* TH1: reload value for 9600 baud @ 11.0592 MHz */ TR1 = 1; /* TR1: timer 1 run */ TI = 1; /* TI: set TI to send first char of UART */ do{ P1 = P2; printf("i got a pocket full"); putchar(0x20); for(j=0; j<255; j++); { for(i=0; i<255; i++) { _nop_(); _nop_(); } } printf("yyyyyyy\n\n"); }while(1); } Any suggestions as to what I should try would be appreciated. Thanks.
Im not an C51 expert, but I do not see a pin set as output anywhere. Best regards, Niels
You don't need to set pins as output, they're all pseudo-bidirectional. You write out to them an they'll attempt to drive that level (port 0 is open drain so you'll need a pull-up, actually, I often pull all my ports up). To read a port just write a one to the pin and then read it. For the UART and TxD the pin just works as an output, nothing for you to do. It's not like the PIC.