I have a pin P2.0 that is set as a carrier detect input. When the pin goes low this starts my timing routine which monitors the incoming data on P2.1. The data rate is 300 baud so I set up a timing routine to basically bit bangs the incoming data at a 300 baud rate. I have include a bit of the code that does this timing routine. I did not come up with this code it was something I found on the net, I just modified it to fit my need. This is still a learning process for me.

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RXBIT set P2.1 ;Receive LTR data on this pin
CARDET set P2.0 ;Detect incoming carrier

;The serial baud rate is determined by the processor crystal, and this constant which is calculated as: (((crystal/baud)/12) -5) / 2

;BITTIM EQU 45(11059200/9600)/12) -5) / 2)= 45

BITTIM EQU 1533 ; Set for 300 baud

START: MOV R1,#8
K0: JNB CARDET,$

K1: MOV R0,#BITTIM ;Wait full bit-time
DJNZ R0,$ ;For DATA bit MOV C,RXBIT ;Read bit RLC A ;Shift it into ACC
DJNZ R1,K1 ;read 8 bits
CJNE A,#0ACH,START ;Sync pattern was received
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I have the code set right now to only read the first 8 bits. If this works I will then work on reading the 9th bit.
I am sure there is a better way to do this, so I am open to any suggetions to make this better.

Craig