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Diagnosing Hardware Error Detecting Circuits

IP.com Disclosure Number: IPCOM000075568D
Original Publication Date: 1971-Oct-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Lutter, EP: AUTHOR [+2]

Abstract

On-line tests (OLT's) test operating capabilities by initiating sequences of commands in I/O subsystems. Operations are chained with a SET DIAGNOSE channel command. A described sequence of steps takes into account the operational characteristics of an I/O controller (CU) in a magnetic tape subsystem, to diagnose CU's ability to detect and report hardware errors in real time.

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Diagnosing Hardware Error Detecting Circuits

On-line tests (OLT's) test operating capabilities by initiating sequences of commands in I/O subsystems. Operations are chained with a SET DIAGNOSE channel command. A described sequence of steps takes into account the operational characteristics of an I/O controller (CU) in a magnetic tape subsystem, to diagnose CU's ability to detect and report hardware errors in real time.

CU is designed to respond to a SET DIAGNOSE channel command having a CCW (channel control word) with the loop-write-to-read (LWR) bit active, to subsequently receive only write operations. In other words, a write operation must always follow a SET DIAGNOSE having an LWR CCW.

To test the hardware error-detection circuits, a control command involving readback operations is chained to a SET DIAGNOSE having an LWR CCW. For example, such a control command can be forward space record (FSR), backward space record (BSR), or FILE OP. Such a sequence of commands causes the supervising microprogram in CU to be in a write mode with the hardware or data flow circuits which process signals being in the read mode. As a result, the data flow circuits generate no write clock. The microprogram, which is in the write mode, expects a write clock and responds by indicating a hardware error, i.e., absence of a write clock during write mode.

The sense data obtained from the above-described sequence of channel commands are CUE (control unit end), DVE (device end), UCK (un...