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Diagnostics for a Synchronous I/O Control Unit Attached to a Microprocessor

IP.com Disclosure Number: IPCOM000080690D
Original Publication Date: 1974-Jan-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 2 page(s) / 36K

Publishing Venue

IBM

Related People

Ballou, DC: AUTHOR

Abstract

A synchronous I/O control unit attached to a microprocessor can be diagnosed for errors by using two diagnostic programs. One program loaded in the CPU is run online while the other, which is a microprogram, is run offline. The figure shows the hardware necessary to provide an interface between the microprocessor and the I/O unit. This allows the microprocessor to simulate the CPU while operating offline.

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Diagnostics for a Synchronous I/O Control Unit Attached to a Microprocessor

A synchronous I/O control unit attached to a microprocessor can be diagnosed for errors by using two diagnostic programs. One program loaded in the CPU is run online while the other, which is a microprogram, is run offline. The figure shows the hardware necessary to provide an interface between the microprocessor and the I/O unit. This allows the microprocessor to simulate the CPU while operating offline.

The offline diagnostic microprogram steps through all possible sequences that can occur on the I/O interface. The I/O, in turn, communicates with the machine control logic during normal operation. The micro-program checks the responses on the normal I/O to machine control interface, as well as the I/O responses on the offline diagnostics interface. If each response is proper, the diagnostic microprogram proceeds to the next step in the program. When an improper response from the I/O on either interface is detected, both the I/O and microprocessor are stopped on the error by stopping their respective clocks. No mechanical motion or device action occurs during the running of the diagnostic program.

When an error occurs, it is possible to find the replaceable unit that has failed by referring to a Maintenance Analysis Procedure Manual. This manual contains charts of diagnostic microprogram addresses indicating which pins to probe. Knowing the address at which the error occurred, along with...