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Fleshing out Instruction Set

A project log for 8 Bit Breadboard CPU

A home-brew 8 bit Microprocessor built on a breadboard 64K Address Space, IRQ, and DMA 16 Bit Stack Pointer, 4 8 bit Registers or 2 16 bit

2-Zons2-Zons 12/09/2018 at 10:072 Comments

I updated my instruction list using different addressing modes and the new ALU functions.  I am over by 57 Instructions.  Going to have to do some prioritizing.  I can't beleive they didn't even use all 256 Instructions on the 6502 and others.   I guess when they were drawing all the microcode manually on massive film, walking on it with their socks it kind of makes sense.

https://docs.google.com/spreadsheets/d/1kbxYGDeIOszgvjPYRdes-bELOBlojT_tjxe_RD9MVUQ/edit?usp=sharing

Added schematic for program counter

https://upverter.com/2-Zons/28ed54fb010b5ac1/Program-Counter-16-bit-Register-for-8-bit-TTL-CPU/

Discussions

Yann Guidon / YGDES wrote 12/09/2018 at 11:46 point

In your PC diagram : the DOWN inputs of the '193 are left open... That would work for LS but not when you switch to HC or HCT.

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2-Zons wrote 12/09/2018 at 22:24 point

Fixed

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