Hi,

I want to read/write to an external memory.
My problem is that the /RD and /WR - Pins of the µC aren't free!!
That's why I want to write my own movx-routine.
But I don't really know how to do that.



READ:
(PIN_DATA = Port0)
(PIN_CONTROL = Port2)(/WE /OE /CE x x x x x)

mov PIN_CONTROL, #E0h; -CE=1 -OE=1 -WE=1

clr PIN_N_CE; -CE=0 -OE=1
clr PIN_N_OE ; -CE=0 -OE=0
mov a, PIN_DATA; -CE=0 -OE=0 ; HERE?
setb PIN_N_OE ; -CE=0 -OE=1
mov a, PIN_DATA; OR HERE?
setb PIN_N_CE1 ; -CE=1 -OE=1



Do I also need some wait-cycles or NOP?? And at which point can I read data?
And how can I write data to the external memory??
(I use 89S8252)