Abstract: A station for a network using a DQDB communications protocol. A counting unit for maintaining an erased count of erased slots, an erasing unit for determining, erasing and outputting slots received on a transmit bus which have been used to transmit data to and have been received by an intended destination on the transmit bus are used. The erased slots are thereafter available for use by stations for data transmission on the transmit bus, and for determining if the erased count is greater than a predetermined value when a request for a slot is received by the station on a request bus and for erasing the request when the erased count is greater than the predetermined value. The erase count may be incremented by the station when a slot is erased by the station. Alternatively the erase count of a station may be incremented only when the station uses an erased slot to transmit data to another station.

Abstract: A communications method for a shared-medium communications network having a plurality of stations connected by a first and second bus. The first bus is for data transmission in one direction and the second bus is for data transmission in an opposite direction. The method includes transmitting data between stations in slots. A station desiring to transmit requests the use of a slot by placing a request signal on the bus in a direction opposite to the desired direction of transmission. A slot is then used on a first request, first use priority except for a least one station which is allocated a slot without regard to the first request first use priority. This allocation provides for guaranteed bandwidth traffic.