Hi All, I have a problem with this code: This simple code sends 0-255 with 9600 baudrate to pc and P2 port My problem is in loop runtime . program crashes when arrived to line :P2=i. so we see '0' only on hyperterminal . I changed type of 'i' to int , but the result remains . All The Best Aziz #include <w78e65.H> #include <stdio.h> main() { unsigned char i; TMOD=0x20; SCON=0x52; TH1=0xfa; TR1=1; for(i=0;i<=255;i++) { printf("%d",i); P2=i; } } /**************************************/