BRIAN J SARGENT
Radio and Television Technicians in Dunstable, MA

5101150, Mar 31, 1992

Feb 22, 1991

7/660289

Robert C. Sullivan - Stow MA
Brian J. Sargent - Dunstable MA
Robert H. Pincus - Andover MA
Rudy D. Pietrantoni - Natick MA

GenRad, Inc. - Concord MA

G01R 102

324158F

An automatic circuit tester (10) employs a scanner (20) embodied in a group of interconnected scanner boards (46, 47) that provide switching by means of mechanical relays. The scanner boards plug simultaneously into respective instrument boards (44) and into a common scanner bus (50) separate from an instrument bus (38) that carries the signals that control the instruments on the instrument boards (44). The scanner bus provides a common pathway for signals to travel between instruments or system pins to which one scanner board is connected and those to which another is connected. It also provides scanner-control paths so that the instrument boards to which the scanner boards are connected to not need to provide such paths and thus do not need to be custom-designed for the particular tester in which they are used.

4569048, Feb 4, 1986

Sep 19, 1983

6/533444

Brian Sargent - Dunstable MA

GenRad, Inc. - Concord MA

G06F 916, G06F 1100

371 16

A microprocessor-based system (10) is tested by a testing device (32) that substitutes instructions from a substitute memory (38) for those in the main memory (28) of the system (10) under test. When the processor (12) of the system under test attempts to read a location in its memory (28), it places signals on bus address lines (22) to designate the memory location and places a data-direction signal on a control line (50) to indicate that the memory (28) is to transmit rather than receive information. In ordinary operation, the memory then places its data on bus data lines (24). In order to replace the data from the main memory (28) with data from the substitute memory (38), the testing device (32) senses whether the address lines (22) carry the address of a memory location whose contents are to be substituted. When such an address is detected, it overdrives the control line (50) to cause it to indicate a write rather than a read. This prevents the main memory (28) from placing its data on the data lines (24).