I think it would be a good idea if you posted your schematic.
clk is connected to pin 53, and the arduino sketch sets the 53 pin down, up 100 ms latter, then again up 900 ms latter, to get a 1 hz frequency)
But the Z80A started to get very hot
I've had hard times to find it, I'd rather not burn it!
when I spy the addresses required by the Z80A,
I've just written a program for the arduino to send 0xC3 (JP) when the 0 address is requested, or 0 for any other address, so it will code a JP 0 and forever loop.
You can't supply a clock signal to the Z80 from an IO port, you need a high frequency, about 2-4MHz.
It brings back memories.
How sad is that?
I had a Microprofessor development board