Sharp MZ80B – Boot-Disc, RAM/ROM-Disc, YM2149 Sound

After cleaning these old computers, I decided to create a first card for those systems – hoping, that they might work:

Sharp MZ80B, Boot-Disc, RAM/ROM-Disc, Sound

Summarize:

a) The YM2149 is located at 0x60/0x61 and is feeded by the 4 MHz system clock (therefore a AY8910 will not work)
a.1) One port of the YM2149 is feeding LEDs
a.2) One port of the YM2149 is used for switches (for own software )

b) The right part is the MZ80B Boot-ROM Disc, which contains a 32KByte ROM. Press “/” during IPL-RESET and then the software will be loaded from the ROM and started (proof of concept was here Disc BASIC 6510 with Monitor 1510)

c) The left part is a copy of the MZ1R18 RAM file card, it did not work at the beginning, because I used the original port addresses of the MZ800 and well I was not aware, that the Z80PIO A of the “B” is already there located. So I changed the address to 0x6A, 0x6B’to make them work. In addition to this one has 8 pages of 64K RAM and 8 pages of 64K ROM. (the pages can be selected at 0x6C).

So, the general idea is to have a selection program in the Boot-ROM disc and from there I can select up to 16 programs located in ROM (or however it is located within this ROM).