Fix for ROM Emulator 1.1 Mega boards

A project log for ROM-emulator

Emulate a small size ROM with a RAM and Arduino with Intel-HEX interface

fjkraanfjkraan 07/07/2021 at 06:580 Comments

The 1.1 board did seem to work in some conditions, but wasn't really universally usable. This is a fix for the board, making it compatible with the 1.3 design. I didn't need more boards, so haven't really ordered and build any 1.2 or 1.3 for testing. The modification for 1.1 described here does work.

- replace the 74LS02 at U2 with a 74LS27
- cut trace to U2-1
- cut trace to U2-2 (component side)
- cut trace between U2-6 and U2-7
- cut both traces to U2-12
- cut trace between U2-8 and U2-9
- connect U2-9, U2-10, U2-11 to U2-7 (unused port)
- connect U2-1, U2-2, U2-13 to U2-6
- connect U2-4 to U6-7 (H1, buffered board OE*)
- connect U2-5 to U5-1 (H0, buffered board CS*)
- connect U2-12 to U3-19 (board read)

See the boardPatch1.1to1.2.jpg image