Media access controller with a shared class message delivery capability

Abstract

Activity on a digital communication network is divided into periodic intervals, that are further subdivided into first and second phases during which different classes of data are transmitted. A media access controller for a station on the network has an interface that connects to an external device which supplies first and second classes of data for transmission over the network. A first memory stores the first class of data and a second memory stores the second class of data. The external device supplies a third class of data that may be transmitted over the network during either the first or second phases. The third class of data is held in a third memory. A transmitter connects the three memories to the interface in order to send data over the network. A control circuit regulates the transfer of data from the memories to the transmitter, with data being transferred from the first memory when the media access controller has access to the network during one of the first phases. Data is transferred from the second memory when the media access controller has access to the network during one of the second phases, while data in the said third memory is transmitted when the media access controller has access to the network during either of the first or second phases. The transfer of data is governed by three pointers that indicate the amount of data within the memories that has been released for transmission by the device.