MegaCD-Connect-BD-Remake

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MegaCD-Connect-BD-Remake

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A Remake of the MegaCD Connect BD Logic Board, Targeting the 315-5477 (MCE V1) MegaCD

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# MegaCD-Connect-BD-Remake
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.

![PCB](https://raw.githubusercontent.com/Board-Folk/MegaCD-Connect-BD-Remake/main/images/PCB.png)

* 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 The ATF Works, but i also see this is obsolete.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 2.3 Changes:-

Updates to Kicad v9, Changed A26/B26 on the CD Expansion to point to 9v, and not 5v. Made no difference with the older version, but made it now match the original PCB.

Added new Logic version, because GALasm was updated and was giving a different compiled version that does not work. Found what i needed to change to make it work.

You can use either Pre-Compiled Jed Files, for the GAL22v10 / ATF22V10

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

### Compiling The Logic
---

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
```

### Fitting the Board
---

**1. Post**

---

There is a slight modification required to make the PCB fit in the original housing.

![PCB](https://raw.githubusercontent.com/Board-Folk/MegaCD-Connect-BD-Remake/main/images/POST.jpg)
<br>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.

### BOM

---

| 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   |

[**Interactive BOM**][IBOM]

## Thanks

With thanks to @fabiodl for decoding the logic of the Peel IC

* https://github.com/fabiodl/peelDecoder

#### Other Resources

* https://circuit-board.de/forum/index.php/Thread/25582-SEGA-MEGA-CD-1-Reparatur-PEEL-18CV8-PLD-auslesen/

* https://www.eevblog.com/forum/projects/help-with-reverse-engineering-unexpected-behavior-of-peel18cv8-223204/

### !!!!! WARNING !!!!!

Use at your own risk. I accept no responsibility.

[IBOM]: http://htmlpreview.github.io/?https://raw.githubusercontent.com/chris-jh/MegaCD-Connect-BD-Remake/main/bom/ibom.html

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