The Enhanced Diagnostic Module (EDM), model 621-0021, provides the Logic Manager System with additional system monitoring capability such as detection of problems with data and control lines on the I/O bus. It should be assigned a quantity of eight I/O addresses and should always be placed in the leftmost slot (A) of a Parallel or Serial I/O card file.

A four-position DIP switch module on the top left edge of the EDM board sets operating parameters. Switches 1 and 2 select the Watchdog Timer, and switch 3 selects Parallel or Serial I/O operation. Switch 4 selects the way the EDM reacts to a fault.