Browse Prior Art Database

Automatic Data Handling

IP.com Disclosure Number: IPCOM000035177D
Original Publication Date: 1989-Jun-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 3 page(s) / 63K

Publishing Venue

IBM

Related People

Lebrecht, LA: AUTHOR

Abstract

Data transfers between storage and the control unit of a data processing system are normally controlled by microcode. Such transfers can be handled automatically in hardware on a buffer chip, resulting in enhanced performance, as described in the following.

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Automatic Data Handling

Data transfers between storage and the control unit of a data processing system are normally controlled by microcode. Such transfers can be handled automatically in hardware on a buffer chip, resulting in enhanced performance, as described in the following.

There are two methods for transferring data from storage to the control unit. In the first method the device sends data requests for the buffer chip to decipher. The amount of data requested is stored in a request count register.

A counter is incremented with each request received and decremented with each request processed. The channel cannot handle more than a predetermined number of outstanding requests.

The request count and the channel command word (CCW) count registers are decremented as each byte of data is transferred. The buffer chip continues to send data until these registers are exhausted.

In the second method the request count represents the amount of data that has been sent over the channel but has not yet been written to the control unit (CU). A request count register is initialized to zero, and is incremented with each byte of data that is transferred.

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The device responds with a "write data sent" count, the amount of data written to the CU, which is subtracted from the request count. Data is sent as long as the request count does not exceed a set maximum buffer size until the CCW count is exhausted.

When data chaining, an additional request count register is used after the original request count and CCW count have been exhausted. When the device r...