The Digital488 is a digital input and output interface to the IEEE 488 bus. Each unit has 40 TTL level digital I/O lines, which are divided, into 5 eight-bit ports. Each port is software programmable as input or output. The Digital488 has several features, which give it versatile interface capability. A trigger output signal is asserted on the Group Execute Trigger (GET) command. Edge-triggered inputs can generate a Service Request on the bus. Six data formats are software programmable, including ASCII hexadecimal, ASCII character, ASCII binary, binary, high speed binary and ASCII decimal. There are also individual bit set and bit clear commands. Programmable terminators are provided to facilitate interfacing to various controllers.