Hi Rob,
I took your advice and made the following changes to the sequence

?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,P2 ; Read least significant nibble on port2 and store it in Rx_data by
ORL A,#0F0H ; moving the port value into the ACC, then masking off the value of the

ANL A,P2 ; control lines, so you're left with just the data.
MOV Rx_data,A

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

SETB RXA ; Force RX-Accept back to high to acknowledge
; that data has been read


; Repeat steps for higher 4-bit
?WHILE8:
JB RXR,?WHILE8 ; Wait for RX-Request to go low, transfer request from SP2
CLR RXA ; Force RX-Accept to go low
MOV A,P2
ANL A,#00FH ; Read least significant nibble on port2 and store it in Rx_data by
ORL A,#0F0H ; moving the port value into the ACC, then masking off the value of the

ANL A,P2 ; control lines, so you're left with just the data.
ADD A,Rx_Data ; Add high nibble to Rx_Data



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


SETB RXA ; Force RX-Accept back to high to acknowledge
; that data has been read

END

I went through the code by hand by noting the relative accumulator, port & register values. I am testing it by sending AAh but when i go through this receive sequence i am not gettin 10101010 in Rx_Data. Any suggestions where i could be goin wrong.
Declan.