i make a small program which includes initializing the baud rate, serial port1 control and what mode it would operate. I also include this: mov a, #33h mov scon1, a mov a, #00h mov a, scon1 when i run the simulation, #33h was put to the accumulator and it was transferred to sbuf1..and the accumulator was reset to 00h. However, it didn't get 33h from sbuf1 back to accumulator. and i wonder why???