Shared Projects by KI5NYZ

Provides 4 virtual 32K EPROM from a single 128K flash chip, in a Molex 78802 form factor to fit in a Molex 78805 socket.

The pinout at the castellated edge contacts is the non-standard pinout for the TRS-80 / TANDY Models 100, 102, and 200.

NOT for EPSON PX-4, PX-8, TANDY 600, Kyotronic KC-85, Allen-Bradley PLCs, Intermec or Telexon hand terminals, or anything else that has a Molex 78805 socket with a standard pinout. For those, see M4ROM_27256

The chip is written and re-writable using this programming adapter common to both M4ROM_TANDY and M4ROM_27256.

Carrier: http://shpws.me/SGGB

Requires an SOIC-28 test clip for programming.

This is ONLY for TRS-80 Model 100, 102, or 200, because of the non-standard pinout.

For other applications that use the same socket but with a standard pinout (TANDY 600, Epson PX-8, PX-4, etc), see the “Meeprom” version from the same git repo if you want an electrically re-writable module, or just use a plain 27C256 on the standard DIP-28 version of the carrier.

Assembly notes:

For battery holders BT1, BT2, BT3 (NOT BT4!) break the rear walls off before soldering, so that a battery can pass all the way through the holder. Flush-cut everything on the top side as close as possible, and re-flow the cut posts to smooth them into domes. Optionally solder 2 short bits of wire from the two exposed vias to the rear walls of BT4 to mechanically strengthen those walls. Solder a 25mm piece of 0.6mm solid core insulated wire to the GND side of the big yellow capacitor on the REXCPM.

Qwiic adapter wire connections:

BLACK -> new GND pin on the large yellow cap

RED -> pin closest to the cap

BLUE -> center pin

YELLOW -> pin furthest away from the cap

8K RAM module for “Model T” computers.

How to do the legs.

https://gist.github.com/bkw777/52d85d89eeff8445cc667685d05ea94d

Don’t use square pins. They are too fat and they damage leaf-style sockets. Even standard machined round pins are a bit too thick technically.

Writable replacement for main rom in TANDY 102, TANDY 200, NEC PC-8201, Olivetti M10, Kyotronic KC-85

http://tandy.wiki/FlexROM_102

Optional breakout send/return for /CS line, for use with REX_Classic Main ROM Management Feature

This version is NOT for TRS-80 Model 100 !

For Model 100, use https://www.pcbway.com/project/shareproject/FlexROM_100.html

How to do the legs

To program the chip, just place the board directly into a programmer and set the two smaller jumpers.

(Does not require a programming adapter. The jumpers change the pinout to match the IC, so the board is it’s own programming adapter.)

You can find rom images at http://tandy.wiki/Model_T_Y2K

BOM verified by John Hutchison 2025.1.15 https://www.digikey.com/en/mylists/list/5FEBN35SNT