Skip to main content

GameBoy (Classic) Work In Progress

This is a dump from the's notes on an in progress GameBoy hack. I will refine it later.

Forum thread is here.

I'm trying to identify and spec out the LCD signals in the GB (classic). I'm looking to do away w/ the GBs original controller board while keeping the LCD board.

Basically I want to plug the ribbon cable into my on PCB and output the necessary signals to drive the video myself.

I'm just wandering if anyone has more info on LCD signals output by the z80 so I can emulate them to display stuff.

So far I've mapped all the buttons, speaker, power LED, LCD negative power to the appropriate pins on the ribbon cable.

What I have so far:
Note: Pin 01 is the pin on the ribbon cable closest to the power switch (at the cables connector).
Note: Pin LCDV1 is the pin closest to power switch on the LCDs vertical axis connector (beneath LCD).
Note: Pin LCDH1 is the pin closest to power switch on the LCDs horizontal axis connector.

Pin 01 GND
Pin 02 Power LED - (Unregulated Batteries Voltage)
Pin 03 LCD Drive voltage (-19 V) This voltage comes from the voltage converter attached to the CPU section.
Pin 04 Left & B buttons
Pin 05 Button Diodes 1 & 2
Pin 06 Down & Start buttons
Pin 07 Up & Select buttons
Pin 08 Right & A Buttons
Pin 09 Button Diodes 3 & 4
Pin 10 GND
Pin 11 Vcc - Regulated 5V (different from Pin 02).
Pin 12 VERTSYN (I think) Goes to LCDV8.
Pin 13 ? - Connects to LCDV6 and LCDH7 (Either DATALCH or ALTSIGL)
Pin 14 CLK ? - According to nitro2k01's inverted display mod. Connects to LCDH8. (Data suggests Pin 18 as CLK though.)
Pin 15 DATAOUT1 ? - According to nitro2k01's inverted display mod. Connects to LCDH9.
Pin 16 DATAOUT0 ? - According to nitro2k01's inverted display mod. Connects to LCDH10.
Pin 17 ? - Connects to LCDH11 (Either CONTROL or HORSYNC)
Pin 18 ? - Connects to LCDV10 and LCDH12 (Either DATALCH or ALTSIGL) (Data suggests Pin 18 as CLK but this conflicts with LCD schematic...)
Pin 19 ? - Connects to LCDH13.
Pin 20 Speaker
Pin 21 GND

So I need help assigning Pins 12-19. I also need to know exactly what they do, and whether the controller or the LCD driver chip(s) are the ones switching them.

Basically...the sequence in which to flip bits...

I do have the LCD section schematic from (gameboy2.gif) but it doesn't have the ribbon pinout or explain what the non-obvious signals do.

Here's a bit of captured data from all those current setup doesn't really do time stamping, so it's virtually useless...unless you want to know that 3 frames fits in 7000 bytes: