Browse Prior Art Database

Noninterruptible Data Flags

IP.com Disclosure Number: IPCOM000092005D
Original Publication Date: 1968-Aug-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 3 page(s) / 40K

Publishing Venue

IBM

Related People

Larsen, LD: AUTHOR [+2]

Abstract

If a transmission control unit TCU is used to control data transmission on a full-duplex line, it is necessary to reserve one channel of the TCU for each half of the full-duplex line so that transmission and receipt of data can be simultaneous. In such a system, it is desirable to be able to insert poll data in transmitted messages. However, such poll data must not be allowed to interrupt transmission of outbound addresses or End of Message EOM sequences. Likewise, an interruption of transmission for a polling sequence must be maintained until an end of poll signal is transmitted.

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Noninterruptible Data Flags

If a transmission control unit TCU is used to control data transmission on a full-duplex line, it is necessary to reserve one channel of the TCU for each half of the full-duplex line so that transmission and receipt of data can be simultaneous. In such a system, it is desirable to be able to insert poll data in transmitted messages. However, such poll data must not be allowed to interrupt transmission of outbound addresses or End of Message EOM sequences. Likewise, an interruption of transmission for a polling sequence must be maintained until an end of poll signal is transmitted.

Data is normally transmitted from the CPU to the TCU in eight-bit bytes. Not more than six of these bits are needed for transmission of data over teletypewriter lines. The two nondata bits can be used to indicate data transmissions which can not be interrupted. A first flag bit F1, when received by the TCU, is entered into the control word for the associated line and causes polling to be inhibited. It is reset in the control word if the Write command under which the half of the data over teletypewriter lines. The two nondata bits can be used to indicate data transmissions which can not be interrupted. A first flag bit F1, when received by the TCU, is entered into the control word for the associated line and causes polling to be inhibited. It is reset in the control word if the Write command under which the half of the full-duplex line is operating is terminated or if a nonflagged data character is received to indicate there is no further need to inhibit polling. The second flag bit F2 can be used to inhibit polling on a line for an extended period and is normally reset only when a nonflagged character is received.

In the drawing, Case 1 is a message in which no response from the terminal is needed and comprises a start of message symbol SOM having a figure shift code, a letter H and a letters shift code. This symbol is followed by the address of the terminal to receive the following message and then by an end of address symbol EOA having a carriage return, a letter F and a letters shift code. This prefix of the text cannot be interrupted for a poll sequence and the characters from the CPU are therefore flagged to inh...