Browse Prior Art Database

Data Transfer Between Buffers Using Line Counter

IP.com Disclosure Number: IPCOM000075612D
Original Publication Date: 1971-Oct-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 41K

Publishing Venue

IBM

Related People

Lindsey, RD: AUTHOR

Abstract

For text revision purposes a display may be used with a keyboard/printer having access to an electronic store, which is a recirculating register. The video buffer for the display would be loaded from the recirculating register. If the video buffer is a recirculating shift register with addressing accomplished by the use of a "flag" code, which defines the location at which keyed characters will be entered or from which characters may be printed, the display screen should show text in the vicinity of this flag.

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Data Transfer Between Buffers Using Line Counter

For text revision purposes a display may be used with a keyboard/printer having access to an electronic store, which is a recirculating register. The video buffer for the display would be loaded from the recirculating register. If the video buffer is a recirculating shift register with addressing accomplished by the use of a "flag" code, which defines the location at which keyed characters will be entered or from which characters may be printed, the display screen should show text in the vicinity of this flag.

As shown, a video "port" is inserted in the recirculating register downstream from a first port, at which data is entered into and read from by the keyboard and printer. To determine when to begin transferring data to the video buffer, the line terminating characters are decoded both at the first port and the video port. At power on, the line counter is set to zero and the video buffers are cleared. Thereafter, the counter, is incremented at each line termination code detected at the first port and decremented by each line termination code detected at the video port. Thus the counter will contain the number N of line termination codes between the two ports. When the flag is detected at the first port, the count N is noted and (N-1) line terminations are allowed to pass the video port. Immediately after the (N-1) code, data is transferred into the line 1 buffer until the next line termination code, at which ti...