z80 heatbeat explained

Yesterday I went to my local Hamfest and picked up a few Z80 Processors and other goodies. While reading the datasheet I noticed something. If the data lines for the z80 are held in an active low state I will send the CPU a series of NOP (No-Operation) commands. A quick glance on the internet confirmed this and I quickly breadboarded a prototype. I used a manual pulsar as the clock source, tied data lines down and sent the four least significant bits of the address lines out to some LED’s.

When the CPU came up I was able to pulse and the CPU went through the reset cycle. This is great, I know the z80 works and I’m taking my first steps toward building a computer.

I’ll build a dedicated clock and RTC next.

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