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Channel Processor With Microcode Routines to Run As a Unit Exerciser and to Handle Sense Data From a Unit Directly Without the Processing Normally Performed by Operating System

IP.com Disclosure Number: IPCOM000036501D
Original Publication Date: 1989-Oct-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 2 page(s) / 13K

Publishing Venue

IBM

Related People

Cerul, EJ: AUTHOR

Abstract

When certain faults have occurred in a conventional data transfer between a channel processor and an I/O unit, the "unit check" bit is set in the status byte which the I/O unit sends to the channel as part of the ending sequence of a data transfer. Additional information about the fault is transferred from the unit when the channel executes a Sense CCW (Channel Command Word).

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Channel Processor With Microcode Routines to Run As a Unit Exerciser and to Handle Sense Data From a Unit Directly Without the Processing Normally Performed by Operating System

When certain faults have occurred in a conventional data transfer between a channel processor and an I/O unit, the "unit check" bit is set in the status byte which the I/O unit sends to the channel as part of the ending sequence of a data transfer. Additional information about the fault is transferred from the unit when the channel executes a Sense CCW (Channel Command Word).

The information in the status byte is normally sent to the operating system. The operating system can cause a sense operation to take place by creating (1) the sense CW, and (2) a central processor instruction (e.g., SIOF (Start I/O Fast Release) that causes the channel processor to select the I/O unit and execute the CCW.

Apparatus commonly called a channel exerciser tests the operation of a unit on the bus to the channel processor, and during such a test the channel may receive many status bytes with the unit check bit set. An improved channel exerciser handles the sense operation directly.

The channel exerciser is implemented by (1) a unique microcode load for a channel processor, and (2) several modules of code for a component of the data processing system called the processor controller. The exerciser runs in a limited service partition of the system made up of the processor controller, the channel processor, and the I/O units attached to the channel processor.

The channel exerciser runs conventional routines to test a unit. When the channel exerciser receives a unit check in the status byte from a unit being exercised, it executes the following steps to g...