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Alternate Message Control Words in a Communications Multiplexor

IP.com Disclosure Number: IPCOM000075644D
Original Publication Date: 1971-Oct-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Zvaigzne, G: AUTHOR

Abstract

Communications multiplexors multiplex data received on a number of communication lines into a common main storage. To conserve hardware, unit control words are utilized in conjunction with common control hardware to maintain the control status and to store assembled bytes for each of a number of communication lines. A first unit control word performs byte-to-byte message assembly or message-to-byte disassembly, storage buffer allocation, and a number of control functions. A second control word is provided to perform functions similar to the first control word but from an alternate data address. This alternate control word provides the capability of inserting an output message at any point in an output message stream for each line.

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Alternate Message Control Words in a Communications Multiplexor

Communications multiplexors multiplex data received on a number of communication lines into a common main storage. To conserve hardware, unit control words are utilized in conjunction with common control hardware to maintain the control status and to store assembled bytes for each of a number of communication lines. A first unit control word performs byte-to-byte message assembly or message-to-byte disassembly, storage buffer allocation, and a number of control functions. A second control word is provided to perform functions similar to the first control word but from an alternate data address. This alternate control word provides the capability of inserting an output message at any point in an output message stream for each line. Control is passed to the alternate control word whenever a special bit set aside for this purpose in the first control word is turned on. This bit can be turned on by the programmer. A count is maintained in the second control word and is incremented by one for each byte transmitted. The second control word functions as a duplicate of the first control word except that, when the count reaches zero, it causes the control bit of the first control word to be reset and thus, transfer control back to the first control word.

This is more fully described in IBM System Reference Library Manual "IBM 2969 Programmable Terminal Interchange Model 1, RPQ 88117: Special Feature Descripti...