The PDP-14 was a specialized computer from Digital Equipment Corporation’s Industrial Products Group designed to replace industrial level relay controls for machinery and machine tools that performed repetitive tasks. It was specifically designed to function in the harsh electrical environment encountered in facilities where electric motors, solenoids and arc welders were present, a significant adversity for normal computer electronics. The PDP-14 was specifically designed to be the first level of factory automation, functioning as a programmable logic controller (PLC), through its ability to communicate with a standard DEC PDP-8 minicomputer. The first unit was delivered in June 1969 and used to control a gear grinding machine. Its design as a "programmable machine controller" was patented in 1973. The PDP-14 was designed to process Boolean equations, usually expressed as “ladder diagrams” and as such had a programmable read-only program (PROM) memory. Programs were developed using a PDP-8 then tested using a direct connection to the PDP-14. The PDP-14 was put into a check out mode where instructions were provided by the PDP-8. Following checkout, the PDP-8 provided the instructions to be put into the PROM. Later versions (for example, the PDP-14/30, whose instruction set was not binary compatible) are based on PDP-8 physical packaging technology. There also was a PDP-14/35 and a lower cost/reduced I/O capability PDP-14/L.

Hardware

The 12-bit PDP-14 could hold a maximum of 4K words for instructions. The system's configuration included a control unit and a number of external boxes: Hence the combined usable output address space of the O-boxes, A-boxes and S-boxes was 255 or fewer.

Registers

The PDP-14 has seven 12-bit registers:

Instructions

Among the PDP-14 instructions were: There were also instructions (Test if something is ON or OFF) and instructions (SYN – Set "Y" oN, SYF – Set "Y" ofF).

Software

The original PDP-14 required that programming be done by DEC. Subsequently, software development for the PDP-14 was done on another system, the PDP-8. A PDP-8 program named SIM-14 allowed for simulating the PDP-14.

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