ACID protection chip within a cartridge
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 is a custom creation by Amstrad it is currently not possible to replace this chip nor to build new cartridges, because it is unknown how it works. It is labeled 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
+------+