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HOTLINE A B/SC Access Method

IP.com Disclosure Number: IPCOM000073597D
Original Publication Date: 1971-Jan-01
Included in the Prior Art Database: 2005-Feb-22
Document File: 2 page(s) / 14K

Publishing Venue

IBM

Related People

Hendricks, EC: AUTHOR [+2]

Abstract

HOTLINE is a READ/WRITE level access method which provides processor-to-processor telecommunications support. The HOTLINE access method transfers a block of data when, and only when, the remote (receiving) processor specifically requests that a block be transmitted. That is, the receiver processor rather than the transmitting processor initiates line transactions. In other words, each processor may "read" the output queue of the other processor. HOTLINE is designed to communicate with an identical copy of itself and there is no master/ slave terminal distinction.

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HOTLINE A B/SC Access Method

HOTLINE is a READ/WRITE level access method which provides processor- to-processor telecommunications support. The HOTLINE access method transfers a block of data when, and only when, the remote (receiving) processor specifically requests that a block be transmitted. That is, the receiver processor rather than the transmitting processor initiates line transactions. In other words, each processor may "read" the output queue of the other processor. HOTLINE is designed to communicate with an identical copy of itself and there is no master/ slave terminal distinction.

A WRITE request to HOTLINE is serviced by stacking the buffer address for use in the event of a READ request from the remote processor. A READ request to HOTLINE causes a certain control character sequence to be transmitted over the line to the remote processor. Upon receipt of the control sequence, the remote processor responds by transmitting the data contained in the buffer associated with the oldest outstanding WRITE request. When the block has been successfully received at the processor which initiated the READ, that processor responds with an acknowledgement (a control character sequence) and the transaction is completed. At this time either processor may initiate the next transaction by means of another READ request.

Both READ and WRITE buffers are provided by the caller, and both include an Entry Control Block (ECB) and a count field. The READ buffer ECB is posted by HOTLINE when the READ request line transaction is completed. The WRITE buffer ECB is posted when the data contained in that buffer has been requested, received, and acknowledged by the remote processor. READ and WRITE requests to HOTLINE may be specified "unconditional" or "conditional". Unconditional READ request service is not terminated until the block is made available (via a WRITE request) at the remote processor and successfully received in the READ caller's buffer. Conditional READ request service will be terminated with an error post code if the output stack (containing outstanding WRITE requests) at the remote processor is empty when the remote READ request is issued. Unconditional WRITE r...