How can I send AT commands from the 8051 to the modem. In fact, I want to set the modem to auto answer at the 4th ring. So in AT commands it means "ATS0=4", right? OK. I've tried to send the ASCII chars through serial port using RS232 with an external modem. But it doesn't work. It's a problem with the serial port?
Here's a copy of the program:
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ORG 00H
MOV SCON,#010H
MOV A,#07FH
ANL A,87h
MOV 087h,A
MOV SBUF,#041H ; ASCII of A
MOV SBUF,#054H ; ASCII of T
MOV SBUF,#053H ; ASCII of S
MOV SBUF,#030H ; ASCII of 0
MOV SBUF,#03DH ; ASCII of =
MOV SBUF,#034H ; ASCII of 4

END
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I think it's a problem with the configuration of the serial port, maybe. Or the baud rate is too high to the modem.

Thank's a lot!

Thiago Camargo - (SP - Brazil)