MBC5/CPLD for the GameBoy
This is what the MBC5/CPLD cartridge looks like in the hands of a lousy photographer…. The sram is
completely hidden behind the cable, and the lcd looks like it should be sent in for repair !
The gameboy actually runs a GBDK testprogram which enables functional tests of the MBC5 part and
the CPLD i/o. (see downloads below).
Note that the pcb is an prototype and thus older from what is shown further down this page.
The use of the word cartridge is a little far fetched, as the
pcb is bigger than the gameboy plus the fact that it doesn`t even
fit in the expansion slot, but uses a ribbon cable with a
passive link PCB to connect to the gameboy. Next step could be
to minimize it, but that would require a through-plated pcb.
Digital part consists of a Xilinx CPLD whichs hosts the MBC5
functionality and i/o, a 512 kBytes flash and a 128 kBytes sram.
IDC interfaces besides JTAG and a 5V connector :
Cart connector IDC1 IDC2 To gameboy cartridge slot via link PCB. Karlsruhe/Marc Rawer pinout.
IO connector IDC3 IDC4 All i/o pins from the CPLD including i/0 select and relevant adress signals.
Emulator IDC5 Matches at least Andrew March`s “emul8r”.
All IDC connectors are 34 pins to ensure that even the smallest distraction will have fatal consequences.
The cart have a fixed 5V regulator intended to drive the
cpldcart and a adjustable regulator set to 3V for the gameboy. In
this scenario the current consumption is close to 200mA. The
pocket gameboy uses approx.80mA (at 3V, no sleep) and the
cpldcart approx. 100 mA.
Note that the maximum input voltage is about 12V unless the regulators is fitted with some kind of heatsink.
The external power supply is connected via a 4 pin molex and a
single pin supplies 3V to the gameboy. There is no 5V connection
from the cpldcart into the gameboy (via the link cable) but no
harm is done if it should happen. (!) The 3V must be supplied in
order for the smps in the gameboy to produce the negative
bias voltage for the LCD.
It would be nice to have the opportunity to be able to run
both the gameboy and the mbc5/cpld cart on the normal gameboy
batteries alone (for a short time….), but i haven`t done anything
to check it out yet.
How to build :
Like anything else.
I have no idea what it costs to produce a cartridge as the one shown here. And i don`t care
This is completely besides the point with this project.
If you think that this could be a cheap alternative to a whatever
consumer pirate copier that might exist then I am afraid I will
have to dissapoint you right away. Sorry !
Both the flash and the sram are normal industry standards and
can probably be replaced with anything of similar type.
5 IDC34 (17×2 connectors). At least the one for the link cable are mandatory.
7 pin molex JTAG programming jig.
4 pin molex DC IN, external 200mA DC power supply.
1 pin molex GB 3V, to GB battery terminal or DC input plug.
100nF & 47uF decoupling caps + a few resistors and a LM317 + 7805.
The schematics. It should be apparent that the CPLD is busy
doing everything but hosting the memories.. If this board ever
runs out of connectors….
These contains the three 8bit CPLD i/o ports PORTA, PORTB and
PORTC. The definition of these ports are discussed on cpld page.
The signals IO_CE and A0..A3 are included so that the free i/o
adresses can be used as well. Note that there is no read or write
control signals available on the connector.
tw1o sided PCB intended to be made as single side PCB with
wire links (i.e. enameled wire) instead of copper tracks in upper
Dimension : 160 x 80 mm
The link pcb together with a 34 way ribbon-cable is the
interface betw1een the gameboy and the MBC5/CPLD Cart. The PCB
goes into the cart slot of a unmodified pocket gameboy. It`s
quite long because the IDC connector otherwise would block
for access to the power switch at the gameboy top. Suppose this
actually makes the bulky IDC connector a poor choice, but
The 5V track is by default open to let the gameboy supply its own internal 5V circuits.
The dimensions are 51.3 mm X 90.4 mm but the essential measure
is 47.0 mm betw1een the centers of the outermost gameboy pins.
(the pin spacing is 1.5 mm nominal).
One way to position the link PCB in the gameboy cartridge slot
is to murder a cartridge and use the plastic shells. In this
case the PCB should be 0.8 mm thick. You`ll have to cut away
the `end-piece` in the plastic shells to make it fit.