HIL bus

HIL ("Human Interface Loop"), or HP-HIL, is the name of a computer bus used by Hewlett-Packard to connect keyboards, mice, trackballs, digitizers, tablets, barcode readers, rotary knobs, touchscreens, and other human interface peripherals to their HP 9000 workstations. The bus was in use until the mid 1990s, when HP substituted PS/2 technology for HIL. The PS/2 peripherals were themselves replaced with USB-connected models.

HIL bus is a daisy-chain of up to 7 devices, running at a raw clock speed of 8 MHz. Each HIL device typically has an output connector, and an input connector to which the next device in the chain plugs; the exception is the mouse which has only the output connector.

HIL buses can still be found on HP PA-RISC and one particular model of m68k server.

The HP-HIL bus uses specific 4-pin, 6-pin, or 8-pin SDL connectors, somewhat similar to RJ-45. The bus can reportedly also use a 9-pin D-subminiature DE-9 connector.

Converters that convert HIL to PS/2 are available.

See also:
* [http://abrij.org/~bri/hw/hil.txt HP HIL Linux driver suite]