Browse Prior Art Database

Time Shared Communication With Key CRT Display Terminals

IP.com Disclosure Number: IPCOM000078779D
Original Publication Date: 1973-Mar-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 4 page(s) / 128K

Publishing Venue

IBM

Related People

Bliss, BE: AUTHOR [+3]

Abstract

Character display terminals exemplified in Fig. 1 by block drawing 1, communicate bidirectionally with host central-processing system 2 over time-shared communication channel 3. Character editing and compacting operations are performed by the terminals, upon electronically stored print copy (e.g. questionnaire) signals received from the host. This increases the efficiency of terminal usage of the shared transmission l.

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Time Shared Communication With Key CRT Display Terminals

Character display terminals exemplified in Fig. 1 by block drawing 1, communicate bidirectionally with host central-processing system 2 over time- shared communication channel 3. Character editing and compacting operations are performed by the terminals, upon electronically stored print copy (e.g. questionnaire) signals received from the host. This increases the efficiency of terminal usage of the shared transmission l.

Editing and compacting operations are governed by supervisory control characters supplied by the host. These control characters are interlaced with the electronic copy signals in nondisplayable control lines of the copy field. Control lines are retained in the terminal storage until changed or cancelled by the host. In transmitting edited copy to the host, the terminals delete protected (nonerasable) characters and close spaces between nonprotected (changeable) characters. In nonprotected spaces of the electronic copy field, the terminals are free to erase old characters or blanks and enter new characters or blanks.

The exemplary terminal comprises a disk buffer 4, a keying facility (e.g. keyboard) 5, edit/compaction controls 6 and a linearly traced cathode-ray tube (CRT) display unit 7. Buffer 4 can store at least one complete video frame of electronic copy information, including separate lines of character video signals, character codes (EBCDIC, ASCII, etc.) and supervisory control signals. The disk recording format (NRLI) precludes interlacing of sensing and recording functions within a line tracing interval. Thus writing of a new (keyed) character requires separate buffering, mixing and rerecording of the entire line containing the old (replaced) character.

The electronic copy format is indicated in Fig. 2. Copy lines (rows of display character fields) comprise respective groups of ten interlaced signal lines. Each group contains one character code line (type 4), two control pulse lines (type 3 and type 2) and seven video pulse lines (type 1). The lines are distinguished inter se by indicated prefix (tag) pulse combinations.

Terminal operation and control logic for keying in of a character is indicated in Figs. 3-5. The operation requires at least two electronic copy frame periods. In one period, the character code and control sublines of the appropriate copy line are read seriall...