Original URL : https://www.retrobrewcomputers.org/doku.php?id=builderpages:plasmo:epm240dev:3vz80:3vz80rev1_1
 Snapshot date: 2025-01-27
 Generator    : wayback-archiver

While Z80 is specified for 5V operation, selected CMOS Z80 are capable of running at 3.3V. This mezzanine board hosts such Z80 plus a 512K RAM and plugs on top of the EPM240 development board. The two-board Z80 computer can run RomWBW. This is link to rev0 of 3V Z80 which does not have the local 3.3V regulator.

CMOS Z80 selected for 3.3V operation

512K RAM

512 byte flash embedded in EPM240 can boot RomWBW

ACIA emulation in EPM240

SD card interface

RTC module based on DS1302

I2C interface

RomWBW capable

Local 3.3V regulator adjusted to 3.5V

Boot from embedded 512-byte flash, etc, etc…place holder.

Schematic

Gerber photoplot files

EPM240 design files

RomWBW SD bootstrap code resided in EP240's embedded flash

EPM240 design files with fast SD bootstrap (6 seconds), but no RAM disk at drive A

Bill of Materials

RomWBW image for 3VZ80. The RomWBW will be booted at power up. It takes 23 seconds to load and boot RomWBW from reset.

Note, Serial port for RomWBW will work without hardware handshake, however to transfer files using XM.COM in RomWBW will require a serial port with hardware handshake capability and terminal emulation that supports hardware handshake such as TeraTerm. The handshake signal needs to be CTS (not DTR). Picture below shows modifications to the common 6-pin CP2102 USB-serial adapter to enable hardware handshake.