US 5,377,189 A · Hybrid data communications systems

Abstract

A hybrid data communication system comprises synchronous line cards(3) and asynchronous line cards(2) connected to a common data bus(1) includes a contention bus(7) arranged to communicate contention signals between the line cards(2,3). The synchronous line cards are arranged to transmit a high priority contention signal to suspend any outgoing transmission by an asynchronous card(3) and to gain access to the bus(1) of synchronous data. The contention bus includes an acknowledgement line(ACK) which is driven low by a receiving line card to indicate that it is receiving data. The receiving line card performs error checking and only receives the acknowledgement when the received data is determined to be error free. In a preferred example, the asynchronous line cards(2) are arranged to monitor the contention line(7) to detect the initiation of a contention cycle by a synchronous line card(3). Subsequently on the completion of the contention cycle the asynchronous cards(2) interrupt ant outgoing transmission of a data frame to allow the transmission of data by the synchronous card(3).

Claims9

Dependent claims

A hybrid data communication system comprising:

synchronous line cards and asynchronous line cards connected to a common data bus including a contention bus arranged to communicate contention signals between the synchronous and asynchronous line cards respectively,
said synchronous line cards being arranged to transmit a first priority contention signal to suspend any ongoing transmission by an asynchronous line card and thus to gain access to the common data bus for immediate transmission via the common data bus of synchronous data;
the contention bus including an acknowledgement line;
and
said synchronous and asynchronous line cards being arranged to transmit a signal on the acknowledgement line while receiving data to indicate that the common data bus is busy, and being arranged when transmitting data to transmit an error checking character and when receiving data to determine from the error checking character whether the received data is error free, and only to cease transmitting said signal on the acknowledgement line when the data being received thereat is so determined to be error free.

2 more elements

Dependencies are inferred from the claim text.

Hybrid data communications systems

Life of this patent

Hybrid data communications systems

Life of this patent

Abstract

Claims9