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Browse Prior Art Database

Measurement Control Unit

IP.com Disclosure Number: IPCOM000074930D
Original Publication Date: 1971-Jul-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 51K

Publishing Venue

IBM

Related People

Hackett, RS: AUTHOR

Abstract

The channel-to-control unit interface (or standard interface) is an excellent place for system I/O measurements, since all of the commands, controls, and responses pertaining to I/O operations are channeled through it. The technique described traps this information as it is disseminated to the various control units, and stores it for future reference as to what actually happened on the standard interface during the I/O operations. The measurement device is completely transparent to the channel, since it looks just like a control unit.

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Measurement Control Unit

The channel-to-control unit interface (or standard interface) is an excellent place for system I/O measurements, since all of the commands, controls, and responses pertaining to I/O operations are channeled through it. The technique described traps this information as it is disseminated to the various control units, and stores it for future reference as to what actually happened on the standard interface during the I/O operations. The measurement device is completely transparent to the channel, since it looks just like a control unit.

The information on the standard interface is serial in nature due to the selection sequence (see diagram). The tag line Address Out signifies that the bus out lines contain the control unit-unit address. At this time, the measurement device can trap the address of the I/O device with which the channel is communicating.

When the addressed I/O unit recognizes its address, it brings up Operational In which is trapped in the measurement device and signifies the start of the time that the I/O unit is connected to the channel. The I/O unit then brings up Address In, and places its address on the bus in lines. This is trapped by the measurement device and compared with the address that was originally put out by the channel to determine if an error has been made. The channel then places the command byte from the first CCW on the bus out lines and brings up Command Out.

The command on the bus out lines is trapped by...