Browse Prior Art Database

Channel Control Unit

IP.com Disclosure Number: IPCOM000078284D
Original Publication Date: 1972-Dec-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 4 page(s) / 67K

Publishing Venue

IBM

Related People

Flinders, M: AUTHOR [+5]

Abstract

In a channel control unit for controlling a number of selector or block-multiplex channels, a main store (MS) scheduler is provided to (a) Examine all requests for storage access and select the one with highest priority; (b) Provide appropriate controls to the storage interface for initiating storage access. (c) Maintain and update a list of current storage addresses for all channels; (d) Determine the end of data transfer by detection of the last address for an operation; and, (e) Accept new data transfer information.

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Channel Control Unit

In a channel control unit for controlling a number of selector or block-multiplex channels, a main store (MS) scheduler is provided to
(a) Examine all requests for storage access and select the one

with highest priority;
(b) Provide appropriate controls to the storage interface for

initiating storage access.
(c) Maintain and update a list of current storage addresses

for all channels;
(d) Determine the end of data transfer by detection of the

last address for an operation; and,
(e) Accept new data transfer information.

The scheduler comprises three associative stores, a Priority and Control Store 10, an Address Store 20 and an Increment/Decrement Store 30, all arranged in a self-controlling subsystem. These are shown in Fig. 1 and operate generally in Search Read or Search Write cycles, in which an input search argument is supplied to a store to access function tables or data registers. The argument can include data read from the store on the previous cycle, as shown for the Priority and Control Store 10.

The Priority and Control store 10 has tables to analyse the outstanding storage requests. In selecting a particular request an appropriate control routine is also selected. Each routine consists in operation control data for stores 20 and 30 and at least part of the search arguments for all three stores. The control data selected is always used in the following cycle.

The Address store 20 holds a list of current addresses and associated data for each channel. This data is accessed when a channel request is selected for a storage access, and it is used to control the transfer, e.g. store/fetch and the updating of the current address, e.g. forward-increment/reverse-decrement. Some of the data, such as key, channel ID, is maintained by the Address store while the address is updated in the Increment/Decrement store. While the address is being updated it is compared to a final address in the Address store, to determine if the data transfer for the Channel Command Word (CCW) is complete. If a compare is found it is signalled to a Unit Control Word (UCW) processor.

The Increment/Decrement store 30 is used to update the address information for the selected channel, by incrementing or decrementing the address during each storage transfer. A bus connecting the Increment/j Decrement store to the Address Store is used for transferring address information. It is also used when accepting new data from the UCW processor. This data is passed through the Increment/Decrement store from bus positions which are reserved for connection and isolation of the path to the UCW processor.

An operation flow chart is shown in Fig. 2. The start condition for the main store scheduler is always the same. All outstanding storage requests are input and analyzed in the Priority and Control store 10. The decision made in the start

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cycle is output in the form of a selected request. In this way, the output of the start cycle control...