Browse Prior Art Database

Poll and Response Method

IP.com Disclosure Number: IPCOM000082473D
Original Publication Date: 1974-Dec-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 39K

Publishing Venue

IBM

Related People

Bhagawan, VS: AUTHOR [+2]

Abstract

In a point-to-point terminal system, a controller 10 often loads a terminal address in a counting register 12, which controls a switch 14 to connect the controller 10 to one of terminals 20. Each terminal 20 may have a plurality of devices such as a keyboard 22 and a display 24. When sending information from controller 10 to a terminal 2O, the serial bit stream from controller 10 to terminal 20 may have the Format A.

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Poll and Response Method

In a point-to-point terminal system, a controller 10 often loads a terminal address in a counting register 12, which controls a switch 14 to connect the controller 10 to one of terminals 20. Each terminal 20 may have a plurality of devices such as a keyboard 22 and a display 24. When sending information from controller 10 to a terminal 2O, the serial bit stream from controller 10 to terminal 20 may have the Format A.

Format A begins with a sync bit, followed by a poll bit of 0 indicating that the message is not a poll, a command modifier bit of 1 if the information being transferred is a command, a plurality of device address bits to identify the keyboard 22 or display device 24 at the particular terminal 20, the information bits themselves, and a parity bit. In the usual case, each message is organized as a fixed format of, for example, 16 bits. In a 16-bit format an 8-bit information byte, a 4-bit device address and 1-bit sync, poll, command, and parity fields can be transmitted.

In those cases when the controller 10 has no information to transmit to terminal 20, controller 10 enters into a sequential polling sequence wherein counting register 12 is stepped sequentially, thereby sequentially selecting terminals 20 in a polling sequence to allow terminals 20 to respond with status information or data information as they require.

In most terminal configurations, the polling and response words also contain the fields used for information t...