Browse Prior Art Database

Use Of The Logic Bit

IP.com Disclosure Number: IPCOM000098563D
Original Publication Date: 1959-Apr-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Vanmechelen, KW: AUTHOR

Abstract

The computer system in the upper drawing is adapted to make use of an information word such as that defined in the lower drawing. This information word contains a sign bit, a group of data bits and a logic bit. The logic bit relates to any two-state condition of which some record must be kept. For example, in real time control systems, it may be desirable to know whether various devices are either on or off. This information may or may not be related to the data bits in the word. In the system an instruction word from instruction memory, 10 is decoded in the program control 11. The command generation portion of the instruction is supplied to the arithmetic unit 12 to set up a desired operation.

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Use Of The Logic Bit

The computer system in the upper drawing is adapted to make use of an information word such as that defined in the lower drawing. This information word contains a sign bit, a group of data bits and a logic bit. The logic bit relates to any two-state condition of which some record must be kept.

For example, in real time control systems, it may be desirable to know whether various devices are either on or off. This information may or may not be related to the data bits in the word. In the system an instruction word from instruction memory, 10 is decoded in the program control 11. The command generation portion of the instruction is supplied to the arithmetic unit 12 to set up a desired operation. The address portion of the word is sent via an addressing unit 13 to select an information word, such as that shown,from the data memory 14. The selected information word is supplied to the arithmetic unit 12 where the sign and data bits may be utilized.

Where a destructive readout memory is used as the data memory 14, the information word supplied to the arithmetic unit is regenerated back into the data memory. The logic bit passes through the arithmetic unit to the program control where it is available as an output. For example, it may be used to cause a program change, or it may be used to perform some system control function.

Storage of a logic bit with an information word in the data memory offers the advantage of being readily addressable. Where...