GameboyAdvanceRomDumper

Arduino Uno based Gameboy Advance (GBA) rom dumper

Timing

Non sequential access / latch address

set RD to high
set CS to high
put address on bus
set CS to low to latch address
set RD to low to put data on the bus
now you can read data from bus

image: Timing Diagram with Program Logic Saleae

Sequential access (address + 1)

If an address has already been set, you can get to the next address as follows. If no address is set, you have to set one as described in section Non sequential access / latch address.

set RD to high
set RD to low to put data on the bus
now you can read data from bus

Connections

We can only put a 16 bit address on the bus with Non sequential access / latch address, because the Arduino has not enough I/O ports. Every address above 16 bit can be reached with Sequential access

The data / address (D/A) bus pins are between CS and CS2. (... RD, CS, D/A 0 ... D/A 15 ... A 23, CS2 ...). We only use D/A 0 to D/A 15.

ROM Pin-Name	Arduino Pin-Name	Atmega328P Port-Name
VCC	3.3V
CLK (unused)	(not connected)
WR	GND
RD	12	PB4 (PORT-B 4)
CS	13	PB5 (PORT-B 5)
D/A 0	2	PD2 (PORT-D 2)
D/A 1	3	PD3 (PORT-D 3)
D/A 2	4	PD4 (PORT-D 4)
D/A 3	5	PD5 (PORT-D 5)
D/A 4	6	PD6 (PORT-D 6)
D/A 5	7	PD7 (PORT-D 7)
D/A 6	A0	PC0 (PORT-C 0)
D/A 7	A1	PC1 (PORT-C 1)
D/A 8	A2	PC2 (PORT-C 2)
D/A 9	A3	PC3 (PORT-C 3)
D/A 10	A4	PC4 (PORT-C 4)
D/A 11	A5	PC5 (PORT-C 5)
D/A 12	8	PB0 (PORT-B 0)
D/A 13	9	PB1 (PORT-B 1)
D/A 14	10	PB2 (PORT-B 2)
D/A 15	11	PB3 (PORT-B 3)
CS2	3.3V
IRQ	GND
GND	GND

Pull-up resistor and open drain output

I'm not a professional in electronics, but I suspect that the following is important.

Since the outputs of the ROM chip can only pull the voltage to 0V and the high state is an open switch that is not connected (floating), the input of the Arduino must be set to a HIGH value via a pull-up resistor. The outputs of the ROM chip are probably open drain / open collector outputs. The Arduino includes pull-up resistors that can be used for this and that can be switched on via software.