Introduction⌗

This is a clone of the original multifont card for the European QX-10. It is based on the original schematic but has been modified to use modern parts. The main difference is that this card is based around the ATMega32 MCU instead of the old obsolete Intel 8039.

Replacing the MCU involved disassembling the original firmware and writing a new implementation of it in C for the ATMega32.

Schematic⌗

As said above the largest change was updating the MCU to use the modern ATMega32. This alone allowed me to simplify the schematic as this replaced not just the original MCU but also let me drop the 2716 ROM and the external crystal oscillator. In addition I replaced the uPD8243 IO expander used to generate the font ROM addresses with a modern SPI based MCP23S17 IO expander.

The other major change I made was replacing the 8 individual font mask ROMs with a single AT27C010 OTP ROM that could hold the entire font data, this not only made the ROM use a modern part but also simplified the decoding logic as well.

Bill of Materials
Ref Description Part
C11,C12,C14-C20 0.1uf Capacitor K104K15X7RF5UL2
C21 100uf Capacitor ESS107M016AE2EA
J1,J2 3 Pin Jumper 68001-103HLF
J3 Serial Header 68001-104HLF
R2,R3 10k Resistor MFR-25FRF52-10K
RN1-RN6 Resistor Network 4608X-102-470LF
U1 74LS245 SN74LS245N
U2,U3,U17 74LS541 SN74LS541N
U4 74LS125 SN74LS125AN
U5 74LS00 SN74LS00N
U6 74LS04 SN74LS04N
U7,U10 74LS74 SN74LS74AN
U8 74LS30 SN74LS30N
U9 74LS139 SN74LS139AN
U12,U13 74LS374 SN74LS374N
U16 MCP23S17 MCP23S17-E/SP
U26 AT27C010 EPROM AT27C010-70PU
U27 ATMega32 ATMEGA32A-PU

CP/M Support⌗

Support for the multifont card was built into Epson’s CP/M 2.2 M1.3 release and Multifont Basic. It is also supported by MML Systems CP/M Plus (3.0) for the Epson QX-10/16.