Homebrew Z80 update

Since I have an old V-Tech children’s toy that is really a Z80 computer I thought I would reverse engineer it and use it as my Z80 system.

So far things have been working well for it. I have removed all of the ribbon cables and replaced them will headers so now it is a single board. I also changed out the clock crystal from 3MHz to 4MHz. With the stock ROM still on the little theme music plays much faster.

The board has 16KB or SRAM but I am planning out a 64KB module board to replace the old chip. Since the board also has a expansion port for carttages I was thinking to make a backplane board to add a PIO, SIO2, video and maybe a real-time clock module. I got a cigar box to use as a case and mounted 16 switches and LEDs to the lid to attempt to control the Data BUS and Address BUS. I have even probed all of the header sockets back to the main CPU so I can add an HD44780 4×20 character LCD until I can get some proper video output. However I can’t do much software wise until I can get a null modem session connected to it. I might try Grant Searel’s BIOS/ROM image and see how it works out.


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