Z80 Computer

I never thought i’d do it.. make a Z80 computer, maybe I had it in my head it was too complicated.. but I have done it.

So far my Z80 is running an LED display using the Intel 8279 display and keyboard controller, interfaces with an ADC the ADC0808 which is a parallel 8 channel 8 bit analog to digital converter.

What I do love about the Z80 is the ability to build it up, add as much memory as you need, as much I/O as you need and if you get one of the more recent Z80s manufactured they can run up to 20MHz.. of course your memory needs to support this speed, but to be honest for most applications i’ll be doing 4MHz is a perfectly good clock speed. The slowest 6116 RAM is 150ns read/write which is about 6MHz (so a chip clocked at this won’t read and write the RAM at this)

I have ’emulated’ the 80s style interface to control chips of that era using an ATMega, data lines, address lines read,write and chip selects. Address can be easily done with a pair of 595s. But using a Z80 gives me a certain feeling of achievement

Things I miss however:

  • In circuit programming, swapping the ROM each time is slow and annoying
  • Easy to do maths in C
  • Arrays in C
  • C functions in general

Things I love

  • designing your own RAM locations, you know what’s going on
  • Lots of chips that look interesting
  • Learning more about logic gates
  • Learning how an MCU works inside, it’s the same really

 

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