Browse Prior Art Database

Data Transfer Between Two Controller Units

IP.com Disclosure Number: IPCOM000081800D
Original Publication Date: 1974-Aug-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 28K

Publishing Venue

IBM

Related People

Evborn, C: AUTHOR [+4]

Abstract

Two substantially identical controller units are usually used for the purpose of reliability, to control a process like the operation of a telephone exchange. In normal operation one of them, say the A-side is active, i.e., controlling the network, while the other side, the B-side is inactive, waiting to take over the control when necessary.

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Data Transfer Between Two Controller Units

Two substantially identical controller units are usually used for the purpose of reliability, to control a process like the operation of a telephone exchange. In normal operation one of them, say the A-side is active, i.e., controlling the network, while the other side, the B-side is inactive, waiting to take over the control when necessary.

When the Printer-Keyboard is used, the data entered from the keyboard goes simultaneously into both controller sides. By using a Printer-Keyboard Adapter (PKA) including a data register, it is possible to transfer data byte-by-byte by write/read of the data register from one controller side to the other.

The operation is as follows, when A-side is requesting transfer and B-side is active. A sends a command to the PKA, when not busy, setting an identifier in the data register and forcing an interrupt in the B-side. B services the interrupt and starts data transfer, by setting first a byte into the data register and at the same time indicating to A that there is data to be fetched. A reads data from the data register and gives acknowledgement to B, saving that it is ready for next data. This procedure goes on until all data has been transferred.

Since the PKA enters the idle mode between each byte, this transfer can take place in time sharing with the entering of data from the Printer-Keyboard.

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