Z88 MMC

 SD card is the best storage last few years. Widely used in cellphones, cameras, laptops and other devices. SD card seems to be a good storage for Z88 too.

I have designed Z88 MMC card as standard memory card for Z88 memory slots. Of course, case needs a small hole for inserting the SD card.

There is no IORQ signal on card's connector so port is mapped to memory area. Anyway, the Z88 has own WR signal with unstable address and data bus on falling edge of WR !!!

Port addressing:

A19=L

A18, A17=H

A13=H (top address bit of memory page)

ROE=L (RD)

WE=L (WR)

SEL=L

Port is inactive while Z88 tests standard cards inserted to Z88.

Flash:

A19=H

ROE=L, or POE=L (RD)

WE=L (WR, Flash needs special unlocking sequence to erase or write data)

SEL=L

Two chips are used as an address decoder, one chip as input port and one as output port.

SD cards need 3.6V (or less), small voltage regulator is also on the board. Powering the card could be switched off.

Prototype 3 boards

Card was designed as a hybrid card. Flash chip is optionally assembled to hold OZ or alternative OS.

PCB is 50mm long (standard cards are 52mm), it needs special case, data for 3D printer available.

BOM

* prefer manufacturer with lower "Maximum Quiescent Supply" value noted in datasheet

** test before soldering, current depends on LED type and producer

Drawings, schematic, layout and software are subjects of intellectual property. Do not share, publish, produce or sell without author's permission.

At this moment, Z88MMC could be used with Z88 ROSE OS.

Thanks to Thierry, the last of the Z88 Mohicans, Z88MMC will be supported by OZ (as Thierry promised).

Z88MMC evolution