CoCoDragonMultiPak

Dragon MultiPak Interface

This repository contains the designs for a Dragon 32/64 multipak interface based closely on the TRS-80 Color Computer multipak system.

The board allows up to four expansion cartridges to be connected instead of the normal single slot.

The original CoCo MultiPak is a poor fit with the Dragon, this design slims down the interface to ensure it will work with the Dragon cartridge port.

The CoCo also includes a -5V rail connection which the Dragon substitutes with an additional +12V rail. Both cartridge pins are unconnected in this design as a precaution

Power Supply

For casual use the +5V supplied by the Dragon PSU should suffice but could become marginal under load. This board includes an independent power supply that can supplement the 5V current supply, or even run a modified Dragon board if additional voltages are not required.

The power board requires either a 12-15V AC input or a 15-18V DC input (polarity of the connector is not important). If 12V is not required (or critical) a lower rated DC power adapter can be used.

By default the 12V rail is rated at 0.5A but the DC-DC converter on the board can easily be swapped for a higher rated compatible component.

GAL Programming

A comprehensive set of source definitions for the GAL 16V8 chip at IC13 are available on github: https://github.com/TheLittleEngineers/CoCoDragon-MultiPakInterface-CC-Multi-Pak_Version_1.2/tree/master/PAL_GAL

The GAL programs have been tested for use in a CoCo but not with a Dragon - memory mapping should be compatible so no issue is envisaged

Until testing is completed and the programming conirmed the GAL programs should be treated as untried in this context.

GAL Equations

Note this is written in CUPL.

AND is &, OR is # and XOR is $

/** INPUT **/
PIN [2..9] = [A7..0];   /* address bus lsb */
PIN 1 = !FFXX;          /* mapped address range */
PIN 11 = RW;            /* RnW */
PIN 12 = E;             /* Quadrature clock E */
PIN 13 = Q;             /* Quadrature clock Q */
PIN 17 = !CSEL;         /* Cartridge select */
PIN 18 = !SLEB;         /* Device select disable */

/** OUTPUT **/
PIN 14 = !DBEN;         /* Enable data buffer */
PIN 15 = !IOR;          /* Read device select latch */
PIN 16 = !IOW;          /* Write device select latch */

/** EQUATIONS **/
FIELD ADDRESS = [A7..0];

MATCH = ADDRESS:[7F];

LATCH = MATCH & E & FFXX;

EN = ADDRESS:[40..7F] & FFXX;

DBEN = EN # SLEB # CSEL;