I am using the following asynchronous sequence to write a byte from a host(ADuC832) to a (RPC)radio packet controller(sp2-433-160):
1. HOST asserts TX Request line low to initiate transfer
2. Wait for SP2 to pull TX Accept low (i.e. request is accepted)
3. Set data lines to output and place LS nibble on the data lines
4. Negate TX Request (set to 1) to tell SP2 that data is present.
5. Wait for SP2 to negate TX Accept (i.e. data has been accepted)

I have come up with the following code to carry out the sequence
i am not sure what to do for lines 2,3 & 4. I would like to send AA hex to the sp2. As far as i know, for the Analog Devices 832 there is no need to set the data lines to output. The least significant nibble is first sent out the data lines and then the 5 steps are repeated for the MS nibble. The nibbles are combined and the sequence repeated for next byte.

CLR TXR
WAITACC JNB TXA,WAITACC

SETB TXR
WAITACC1 JBC,WAITACC1

Am i goin about this sequence the right way and could you help me out with lines 2 -4 and how i may be able to implement this for sending AAhex.
Declan