README

This repository contains all the files to construct a Trapddor
expansion for the Amiga 500. There are some variants available. For
more information see the project website:

     https://www.jm27.de/for-commodore-amiga-500-1-8-mb-2mb-trapdoor-memory-expansion/

One variant uses a universal GARY Adapter (T3), the second one a
spcialized GARY adapter (T4). The T3 variant has as a main benefit
that the GARY adapter can be used with other original memory expansion
boards using a 74'139 to multiplex the CAS lines. The T4 version's
main feature is that there is no exra connection needed between the
GARY adapter and the Trapdoor board. 

Directories:

- doc: some documentation, needs to be extended

- pcb-trapdoor: kicad files for the pcb for the trapdoor assembly,
  both variants
- gal-trapdoor: Source and JED files for the GAL used on the trapdoor board
  CBR5SEL is needed for the T3 variant of the GARY adapter,
  CBR5EX is for the T4 variant
-pcb-gary-sel: the T3 GARY adater, kicad files
-pcb-gary-ext: the T4 GARY adapter, kicad files

- gal-gary: the corresponding GAL files
  GARY-T3: for the T3 variant
  GARY-T4: for the T4 variant

The PLD files can be compiled with WinCUPL available from Microchip. I
would be grateful fo a suggestion of a free alternative.