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Microprogrammed CRT Multiplexer

IP.com Disclosure Number: IPCOM000090785D
Original Publication Date: 1969-Jul-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 42K

Publishing Venue

IBM

Related People

Creamer, MK: AUTHOR [+2]

Abstract

A plurality of cathode ray tube displays is governed by a single regenerative memory storing the display information and utilizing this system for altering the data in the memory.

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Microprogrammed CRT Multiplexer

A plurality of cathode ray tube displays is governed by a single regenerative memory storing the display information and utilizing this system for altering the data in the memory.

Information to be displayed is stored in regenerative memory 3 from which it is supplied to a plurality of display units 5 under the control of display scanner 7. Clock 9 drives free-running binary counter 11 from which the screen address and display address are supplied to address register 13 which governs the operation of memory 3 and scanner 7. Normally, the information stored in memory 3 is regenerated via a data path including And 15 and Or 17. And 15 is enabled by the output of Inverter 19.

When data is to be altered, a signal is supplied to one input of And 21. The address of the data to be altered is supplied as one input to compare circuit 23. The other input to compare 23 is from register 13. When the address to be altered and the address from register 13 correspond, then the second input to And 21 is enabled, the output then causing the output of inverter 19 to go down. One input of And 25 is now enabled. The other input to And 25 is the input data being supplied from the interface equipment. This input data is then passed through And 25 and Or 17 to the appropriate location in memory 3, replacing the information that is previously stored.

Counter 11 aligns bit-for-bit with register 13 except for the fly-back portion which is dead time to allow...