Browse Prior Art Database

Automatic Reset Procedure for IBM 3270 Family Display Stations

IP.com Disclosure Number: IPCOM000034549D
Original Publication Date: 1989-Mar-01
Included in the Prior Art Database: 2005-Jan-27
Document File: 2 page(s) / 60K

Publishing Venue

IBM

Related People

Behrens, LE: AUTHOR [+2]

Abstract

This invention provides for improved operation of IBM 3270 Information Display System displays by forcing a reset after reconnection. A characteristic of the 3274 and 3174 work station control units and the display stations that attach to them is that if the connection between the control unit and the display is broken and then reestablished, the control unit will not reestablish communications with the display until the display station operator causes a power-on-reset (POR) status at the display. This is most often accomplished by powering the display off and back on. This procedure is annoying and was not considered satisfactory error recovery for the IBM 5209 3270-5250 Link Protocol Converter (LPC).

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Automatic Reset Procedure for IBM 3270 Family Display Stations

This invention provides for improved operation of IBM 3270 Information Display System displays by forcing a reset after reconnection. A characteristic of the 3274 and 3174 work station control units and the display stations that attach to them is that if the connection between the control unit and the display is broken and then reestablished, the control unit will not reestablish communications with the display until the display station operator causes a power-on-reset (POR) status at the display. This is most often accomplished by powering the display off and back on. This procedure is annoying and was not considered satisfactory error recovery for the IBM 5209 3270-5250 Link Protocol Converter (LPC). The reason that this operation is required by the 3x74 control units is that they are designed to start communications with a device only when the device shows a POR status. When communications are broken (such as when the cable is reconnected), the control goes back to expecting the POR status. If this status is not present (such as when the cable is reconnected), the control unit will not reestablish normal communications. The 5209 solved this problem as follows: When a display station first responds to a poll command (such as when the display is powered up or when the cable is connected), the 5209 expects a POR status from the display. This is similar to the operation of a 3x74. If the POR status is...