Browse Prior Art Database

Fail Softly Process for CPU I/O Device Interfacing

IP.com Disclosure Number: IPCOM000080708D
Original Publication Date: 1974-Feb-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 2 page(s) / 49K

Publishing Venue

IBM

Related People

Brown, RP: AUTHOR

Abstract

Partial execution of extended I/O commands is permitted between a CPU and an I/O subsystem which contains multiple I/O devices despite inoperativeness of one of those devices, by effectively stripping the commands associated with the inoperative device from the instruction/data train.

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Fail Softly Process for CPU I/O Device Interfacing

Partial execution of extended I/O commands is permitted between a CPU and an I/O subsystem which contains multiple I/O devices despite inoperativeness of one of those devices, by effectively stripping the commands associated with the inoperative device from the instruction/data train.

The process will be described in an arrangement where CPU 10 communicates through its I/O interface 11 with an I/O subsystem, such as the IBM 7414 Interactive Console. This subsystem includes common interfacing controls and decoder circuitry 15, which controls displays on cathode-ray tube (CRT) 16 and/or printer 17. Controls 15 includes a multiple byte buffer for data reading or writing in response to execution of an I/O program in CPU 10. Programs in 10 include in the data transfers to the buffer in 15 appropriate commands for displays on CRT 16, printing on 17 or both.

For the 7414, data in the buffer is always displayed on CRT 16 and can be selectively printed on 17, which is typically an IBM 1053 printer. A typical exchange for an I/O write program presents a write command character, followed by a series of data characters and an end of transmission (EOT) character. EOT is preceded by a print command if the data loaded into the buffer in 15 is to be printed on 17.

Prior to execution of an I/0 program, a printer available interface line from controls 15 is interrogated and an indication stored in CPU 10 as to whether or not print...