This is the Schematics, PCB and Logic for the Mega-CD Connect BD Targeting the 315-5477 (MCE V1) MegaCD.
It is to replace the 837-8327-01 IC BD MEGA-CD CONNECT BD with a failed ASIC to the older Logic version of the board that has the Peel IC.
The board is not a clone, rather a remake as i do not have access to an original logic board version to do an exact replica of traces.
-
The Gerbers have been created using the recommendations from JLCPCB.
-
This board uses a GAL22V10 to achieve the same logic functions as the Peel IC. Jed file is provided. Use a MiniPro to write the Jed file to the GAL Chip.
Notes:-
-
I have used an ATF22V10B-15PC as a replacement for the GAL22V10. The ATF Works, but i also see this is obsolete. There is ATF22V10C range of chips, but stock seems to be low on these.
-
TESTED V2.0 and this worked, but now made V2.2 and is UNTESTED
-
Finally got some GAL20v8 Chips, and they do not work. Think this is a timing issue. So please use the GAL22v10's instead, unless someone wants to take a stab at getting the GAL20v8's to work. (Looks at Steve)
Version 2.2 Changes:-
-
Moved traces around the middle screw holes, just incase screw heads sub against the silkscreen removing it and causing a short against the 5v rail.
-
Moved the IC1 Silk name slightly up.
Version 2.1 Changes:-
-
Moved /TRDIR from PIN 23 to PIN 15, This should make it compatible with the GAL20V8
-
Added GAL20V8 Logic, but does not work.
-
Updated Labels for Tree House Connection, TH1 and TH2
The software i used to make the Jed file was GALasm. It can be downloaded from here https://github.com/daveho/GALasm
Only source files is provide, so you will need to compile GALasm first. I used MacOS to do this, Linux should work and maybe Windows ???
Once GALasm is compiled, use the following command to compile the Logic into a Jed file from within the GAL22V10 folder.
galasm ./GAL22V10.pld
1. Post
There is a slight modification required to make the PCB fit in the original housing.
This Post would need a little snip to allow the GAL chip pins to sit correctly in the housing.
2. Tree House J3
If you use a Pin Header, you will need to bend it slighly inwards otherwise it will not fit inside the MegaCD.
| Reference | Value | Quantity | DigiKey | Mouser |
|---|---|---|---|---|
| C1 - C6 | 100nf | 6 | CL31B104KBCNNNC | 187-CL31B104KBCNNNC |
| IC1 | GAL22V10B-15 / ATF22V10B-15 | 1 | 556-AF22V10C15PU | |
| IC2, IC3 | 74HC374 | 2 | 296-1592-5-ND | 595-SN74HC374N |
| IC4 | 74ACT10 | 1 | CD74ACT10E-ND | 595-CD74ACT10E |
| IC5, IC6 | 74HC245 | 2 | 296-1584-5-ND | 595-SN74HC245N |
| RN1, RN2 | 9X-1-472LF (4.7K) | 2 | 4609X-101-472LF-ND | 652-4609X-1LF-4.7K |
| J1, J2 | CONN EDGE DF 60POS | 2 | A112392-ND | 571-1-5530841-8 |
| J3 | 2 Pin Header 2.54mm | 1 | 609-4434-ND | 649-77311-118-02LF |
With thanks to @fabiodl for decoding the logic of the Peel IC
Use at your own risk. I accept no responsibility.