Some z80 Progress

Waiting for parts for my Homebrew Z80 Computer is like watching paint dry or grass grow. I got my Zilog Z804C0020PEC chips in a week ago and finally bread boarded a test circuit that puts the CPU into NOP (No Operation) mode. It just does an endless count,  with a 555 Timer and some LEDs on the Address pins you can see the count.

I found the test circuit from this site.

I also have on my Bread Board a typical Crystal oscillator running at 4MHz but you can’t see the LEDs count away since four million cycles a second can’t be seen with a human eye.

20170624_221100 It’s kinda hard to see the three LEDs on the right are on. I’m using some super old LEDs. The far right is the most significant byte and the left is the least significant byte.

So I have a good working CPU. Now to find a way to test other parts and then start planning on a PCB.

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