testing 6550s outside a 6502 bus

Hi all,
as I'm repairing a 2001 320008 assy, I'm trying to test the 6550s and
6540s on a microcontroller board that I've made.
I would use a real 6502, but I've only one spare left, so that's not
an option :)

It seems that the 6550 latches the selects, address and R/W line (for
example lowering R/W after PHI2 L->H always results in a read cycle)
on the rising edge of PHI2, but still I can't make a correct read or
write cycle.
Did anyone succeed in reading/writing these outside a 6502 bus?
We can continue in private chat if anyone...
Best regards

Frank

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