A bi-directional single conductor interrupt line is used in conjunction with a master only initiated data communication bus, to allow a slave device to submit a slave service request to a master device and to acknowledge master service requests from the master device. When not submitting a master service request, the master device maintains an interrupt line voltage at an idle state voltage by setting the interrupt line voltage through a pull resistor. The slave and master devices submit service requests by respectively driving or pulling the interrupt line voltage from the idle voltage to the service request voltage. The slave responds to a master service request or initiates the master servicing of a slave service request by subsequently driving the interrupt line back to the idle state voltage giving a slower slave ample time to prepare for a pending master initiated data transaction. The master detects the change in the interrupt line voltage from the request to the idle state and communicates to the now readied slave device through the data communication bus.