Browse Prior Art Database

Expander for Storage Access Channel

IP.com Disclosure Number: IPCOM000076214D
Original Publication Date: 1972-Jan-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 56K

Publishing Venue

IBM

Related People

Elliott, JC: AUTHOR [+2]

Abstract

Expansion of the accessing capability to input/output (I/O) devices connected to a computer storage access channel is provided. Each of the expanded channels provides all of the I/O data, timing and control found in the original channel and assigns cycle stealing and interrupt priorities. No two of the expanded channels can be performing an I/O operation at the same time.

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Expander for Storage Access Channel

Expansion of the accessing capability to input/output (I/O) devices connected to a computer storage access channel is provided. Each of the expanded channels provides all of the I/O data, timing and control found in the original channel and assigns cycle stealing and interrupt priorities. No two of the expanded channels can be performing an I/O operation at the same time.

Data, timing and control signals are brought on bus 1 from the storage access channel to line terminators 2 and are passed through parallel buses 3, 4, 5 to transmission line drivers 6, 7, 8. An output bus 9, 10, 11 is provided to each of the expanded storage access channels A, B, C.

For cycle-steal operations on an I/O device such as initiate read and initiate write, a priority is assigned through cycle-steal input line 12 connected to line terminator 13. Priority gates 14, 15, 16 for each of the expanded channels govern the level of priority and through drivers 17, 18, 19 control which one of the I/O devices operates. In this system, expanded channel SAC-A has the highest priority, SAC-B the next highest and SAC-C the lowest.

In the retrieval of information, buses 20, 21, 22 are coupled to line terminators 23, 24, 25 and priority gates 26, 27, 28 for each expanded channel. After logical OR'ing under the control of the priority gates, data and control information is provided by drives 29 for entrance into the storage access channel through bus 30.

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