Title: Programmable bus driver isolation

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Abstract: A method of and an apparatus for selectively isolating digital data bus drivers from digital data busses for fault recovery and diagnostic purposes. The digital data bus drivers may be either transistor-transistor logic (TTL) or emitter coupled logic (ECL). For TTL digital data bus drivers, the input voltage (V.sub.CC) is supplied via a switching power transistor. For ECL digital data bus drivers, the ground connection (V.sub.CC1) is made via a switching power transistor. In either case, the switching power transistor is turned on and off in response to one binary bit in an isolation register coupled to the power transistor via an open collector gate or electromechanical switch. By supplying the V.sub.CC (for TTL) or V.sub.CC1 (for ECL) connection to each digital data bus driver through a switching power transistor and controlling each switching power transistor through a different binary bit in the isolation register, the isolation (or non-isolation) status of each digital data bus driver may be controlled via the isolation register to permit the digital data bus to operate notwithstanding failures effecting the state of one or more of the digital data bus drivers connected to it.


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