The Allen-Bradley 1772-M16 memory module is a core memory module that is designed for use with the Allen-Bradley PLC-2/20 and PLC-2/30 processors. It has 16K words of maximum memory capacity and it weighs 1.7 kilograms. This module is situated in the right-most plastic slot in the host processor's chassis. It has 2 diagnostics indicators that are the “STANDBY LOW” and “MEMORY FAULT” indicators. The “STANDBY LOW” indicator is located on the battery pack of the memory module and the “MEMORY FAULT” indicator is located on the front edge of the memory module. The 1772-M16 core memory module has a non-volatile memory that does not lose its stored data when the power is removed from the module or when the module is removed from the chassis slot. The "STANDBY LOW" diagnostic indicator constantly monitors the battery and it flashes on and off when the battery power is low. If the memory fault indicator illuminates, it indicates a memory parity fault that has occurred in the transmission of data between the processor control module and the memory module.

The Allen-Bradley 1772-M16 core memory module is required for the Allen-Bradley PLC-2/20 and PLC-2/30 processor to function but it must be ordered separately from the processors because it does not come with them. There is a front panel which is secured to the processor chassis to cover the memory module and to protect it. The front panel also covers the processor control module. During installation, position and insert the memory module into the designated memory module slot with its label facing upward. The system power must be removed from the memory module before installing or removing a memory segment. When using the 1772-M16 core memory module with the processor, the users must use a separate auxiliary power supply for the I/O chassis.