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Partitioning Data Blocks for Multiplexer Channel

IP.com Disclosure Number: IPCOM000079188D
Original Publication Date: 1973-May-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Heim, LS: AUTHOR [+2]

Abstract

By using the block multiplexer channel on the IBM System/370 a random collection of a field of data from an I/O device such as a 1287 Optical Reader can be buffered and transferred in blocks, rather than one complete field. When capturing noncoded information on the Reader the time between data transfers varies. By using the Command Retry feature (US Patent 3,688,274) of the block multiplexer, the data can be buffered until a block is ready to be transferred. The channel continues to issue chained read commands with the Suppress Length indicator turned off. The last read command will not have a completely filled block. It will break the chain of read commands, exiting back to the user's program.

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Partitioning Data Blocks for Multiplexer Channel

By using the block multiplexer channel on the IBM System/370 a random collection of a field of data from an I/O device such as a 1287 Optical Reader can be buffered and transferred in blocks, rather than one complete field. When capturing noncoded information on the Reader the time between data transfers varies. By using the Command Retry feature (US Patent 3,688,274) of the block multiplexer, the data can be buffered until a block is ready to be transferred. The channel continues to issue chained read commands with the Suppress Length indicator turned off. The last read command will not have a completely filled block. It will break the chain of read commands, exiting back to the user's program.

The use of the Command Retry allows the channel to service other machines when the Reader is not transferring data. This differs from selector channel operation, which requires the Reader to complete the entire field before another device can be serviced.

Conventional use of Command Retry is described in IBM's OEM Information Manual (IBM S/360 and S/370 I/O Interface channel-to-control unit, Systems Reference Library Form GA22-6974-0, Page 29). Presently, devices use Command Retry to seek to a field of data, thus freeing up the channel during seek. This application additionally frees the channel while acquiring the data and then buffering it.

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