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Browse Prior Art Database

Error Indicator for CRT Display

IP.com Disclosure Number: IPCOM000093153D
Original Publication Date: 1967-Jun-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 29K

Publishing Venue

IBM

Related People

Allen, EL: AUTHOR [+2]

Abstract

When a cathode ray tube is used to display the contents of registers in a data processing system, this circuit causes a displayed character to blink when the decoded binary bits have a parity error.

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Error Indicator for CRT Display

When a cathode ray tube is used to display the contents of registers in a data processing system, this circuit causes a displayed character to blink when the decoded binary bits have a parity error.

Register contents are gated to the display, a byte at a time, in the form of eight data bits and a parity bit. The bytes are simultaneously presented to Parity Checker 1 and Character Decode 2. A parity error is manifested by an enabling signal to And 3. The other input to And 3 is provided by Blank Counter 4. The latter is stepped each time the X and Y deflection counters initiate a new sweep X1, Y1. And 5 receives inputs from Inverter 6 and a signal to draw a character and normally causes each decoded character to be displayed.

However, should a particular character have a parity error, the output of And 3 follows a chosen logical output of Counter 4 and blanks the CRT. Depending on the logical combination of the Counter 4 settings, the character can be blanked or displayed for one sweep out of a certain number, or blanked or displayed for a specified number of sweeps. The characteristics of the CRT dictate the logic to use in order to achieve a recognizable blinking of the character.

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