A custom monolithic integrated circuit used as a direct interface between a single-wire data link and microcomputer assemblies in the harsh automotive environment is described. Unusual circuitry allows operation from a single 5-V supply with a grounded substrate despite 6-V ground differences between the nodes. The IC features a 10-mA tristate output with a voltage swing to within 1/2 V of each rail. In addition, the output maintains the high-impedance state during loss of ground and through shorts to -16 and +16 V, remains stable for unlimited capacitive loads, and provides protection from short circuits and high-voltage transients. On-chip waveshaping referenced to an external RC time constant approximates a third-order filter for precise control of rise times and radiated noise in transmitted data. The differential receiver accepts voltage levels from -6 to +12 V and filters input signals for noise immunity. Bit rates to 9600 baud are possible in the described application.
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