Amstrad Cartridge Identification Device

ACID protection chip within a cartridge (bottom)

The ACID (Amstrad Cartridge Identification Device) protection chip is used in the cartridges of the Plus series and the GX4000 game console. Because this chip was a custom creation by Amstrad it is currently not possible to replace this chip nor to build new cartridges, because it is not known how it works. It is labelled with "Amstrad 40908".

Pinout

           +--()--+
       GND | 1  16| +5V
       A7  | 2  15| A6
       CLK4| 3  14| A5
       NC  | 4  13| A4
       CCLR| 5  12| A3
       SIN | 6  11| A2
       |CE | 7  10| A1
       GND | 8   9| A0
           +------+

Pin number	Name	Direction	Description
1	GND	-	Ground
2	A7	Input	Address A7
3	CLK4	Input	Clock (4 MHz)
4	NC	-	Not connected
5	CCLR	?	?
6	SIN	?	?
7	/CE	Input	Chip enable
8	GND	-	Ground
9	A0	Input	Address A0
10	A1	Input	Address A1
11	A2	Input	Address A2
12	A3	Input	Address A3
13	A4	Input	Address A4
14	A5	Input	Address A5
15	A6	Input	Address A6
16	+5V	-	Vcc

Investigation (Spanish language): http://amstradcpc.mforos.com/305097/7723493-que-hace-exactamente-el-chip-acid-de-los-cartuchos/