John Michael Carver

US Patent:

53115244, May 10, 1994

Filed:

Aug 27, 1992

Appl. No.:

7/936812

Inventors:

Lewis R. Carlson - Salt Lake City UT
John J. Carver - Salt Lake City UT

Assignee:

Unisys Corporation - Blue Bell PA

International Classification:

H04L 108

US Classification:

371 70

Abstract:

A fault tolerant three port communications module has two control ports for receiving commands from two computers, and a communications port for transferring data over a communications channel in response to the commands. Each control port includes a select line which carries a select signal with true and false states, mode lines which carry codes that represent the commands, and a write line which carries a respective pulse in sync with each of the codes. The select line, mode lines, and write line of each control port are coupled in the module to a respective inter-processor command decoder having a lead stage and a trail stage. The lead stage detects when a predetermined code occurs on the mode lines and the select signal is false during a first one of the pulses; and, the trail stage generates an output signal that indicates the receipt of an inter-processor command for the module if, during a second pulse that immediately follows the first pulse, the compliment of the predetermined code occurs on the mode lines and the select line is true.