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General Purpose Half Duplex Procedure

IP.com Disclosure Number: IPCOM000074127D
Original Publication Date: 1971-Mar-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 2 page(s) / 56K

Publishing Venue

IBM

Related People

Lebizay, G: AUTHOR

Abstract

This is a general purpose half-duplex procedure for a communication controller which eliminates the need to store as many special routines as it has line procedures in its repertoire. There is an interrupt at the reception of each character. Then the character is processed by a microroutine, the address of which is determined by both the family to which the character belongs and the phase number devoted to the receiving line. The line phase number is the line status which tells the controller which kind of character is expected to come. Moreover, the microroutine updates the phase number of that line so as to prepare the next communication controller channel interrupt on that line.

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General Purpose Half Duplex Procedure

This is a general purpose half-duplex procedure for a communication controller which eliminates the need to store as many special routines as it has line procedures in its repertoire. There is an interrupt at the reception of each character. Then the character is processed by a microroutine, the address of which is determined by both the family to which the character belongs and the phase number devoted to the receiving line. The line phase number is the line status which tells the controller which kind of character is expected to come. Moreover, the microroutine updates the phase number of that line so as to prepare the next communication controller channel interrupt on that line.

Whenever a character is received by the communication controller, there is an interrupt and the character is stored within a register A as shown by Fig. 1. Each character is 4-bytes long: . Bytes 1 and 2 indicate the address of the line the character comes from -"line address"-. . Bytes 3 and 4 are devoted to data bits.

The microprogram interrupt uses the line address (LA) to point on the control block of the line involved. This line control block (LCB) contains the phase number of the line the character comes from. The phase number P (0 </- P </- 255) indicates the status of the line and tells the controller which kind of character is expected to come.

The second part of the character, namely the data bits (bytes 3 and 4) enters a table comprising...