Hello to all,
I am using an AT98c52 setup with an 8-bit address/data bus, this is to leave P2 open. A 74HC5573N is used to latch the address it is enabled through a 8-bit decoder 'nored' with the WR signal. My goal is to be able to connect upto 256 8-bit latches. And it appears to work ok using these lines of code.

MOV R0,#00H ;ADDRESS OF I/O PORT
MOV A,#10101010 ;DATA TO SEND OUT MOVX @R0,A

I've have used one port to control a stepper drive. (toggle the control bits)

Now I'm am trying to use I/O port 3 as the address for an Agilent HCTL-2020 to read an optical encoder mounted on the roller that the stepper motor drives. The goal here is to feed the roller a certain distance and stop.

To test this I've setup my test program to make one motor step, read the HCTL, clear the HCTL, subtract off the read pulses from the needed pulses and loop until the needed pulses are decremented to zero or below.
This works but is inaccurate for some reason. I think it might have to do with reading the HCTL.
I always see 16 bit address buses, but never any 8-bit. Is there a reason for this? Or is what I'm doing acceptable?
I have complete code for this if someone wants to look more closely. There is a place where I've added a delay loop after the read of the HCTL and it causes the feed to be 3.25" longer. Which makes no sense to me at all.

Thanks
Jon Ledbetter