I have come up with the following for the receive sequence. There are 3 parts that i am unsure of, these are the two read data parts and the combine nibbles part. I have put them in brackets.

$MOD832

RXA EQU P2.7 ; Output
RXR EQU P2.6 ; Input
TXA EQU P2.5 ; Input
TXR EQU P2.4 ; Output
D3 EQU P2.3 ; Bi-Dir
D2 EQU P2.2 ; Bi-Dir
D1 EQU P2.1 ; Bi-Dir
D0 EQU P2.0 ; Bi-Dir



?WHILE6:
JB RXR,?WHILE6 ; Wait for RX-Request to go low, transfer request from SP2
CLR RXA ; Force RX-Accept to go low
MOV A,Tx_data ; Prepare least significant nibble
ORL A,#0F0H ; by placing it on lower 4 lines of port2
ANL P2,A

?WHILE7:
JNB RXR,?WHILE7 ; Wait for RX-Request high to tell host data
; is present

(ORL A,#0F0H ; Read in data
MOV A,Rx_Data)

SETB RXA ; Force RX-Accept back to high to acknoledge
; that data hs been read


; Repeat steps for higher 4-bit

?WHILE8:
JB RXR,?WHILE8 ; Wait for RX-Request to go low
CLR RXA ; Force RX-Accept to go low
MOV A,Tx_data ; Prepare least significant nibble
ORL A,#0F0H ; by placing it on lower 4 lines of port2
ANL P2,A

?WHILE9:
JNB RXR,?WHILE9 ; Wait for RX-Request high to tell host data
; is present

(ORL A,#0F0H ; Read in data
MOV A,Rx_Data)

SETB RXA ; Force RX-Accept back to high to ack ; that data hs been read

(SWAP A ) ; Combine nibbles within the accumulator
; in their right order by swapping them

END


Do you think this would work, espically in regard to the parts that i have my doubts about.

Thanks,
Declan.