Browse Prior Art Database

Asynchronous Receiver with Character Insert

IP.com Disclosure Number: IPCOM000087272D
Original Publication Date: 1977-Jan-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 34K

Publishing Venue

IBM

Related People

Nagel, DM: AUTHOR

Abstract

Many terminals present as an output an asynchronous stream of bits delineated by start and stop bits. The length of the stream of bits between the start and stop bits is not necessarily fixed from terminal to terminal. Nor is the bit configuration within the stream, that is meant to identify the terminal to the data processing system to which it is attached, necessarily fixed. This device overcomes these problems when attaching an asynchronous terminal to the IBM System/7 processor via the teleprocessing multiplexor module (TPMM) feature.

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Asynchronous Receiver with Character Insert

Many terminals present as an output an asynchronous stream of bits delineated by start and stop bits. The length of the stream of bits between the start and stop bits is not necessarily fixed from terminal to terminal. Nor is the bit configuration within the stream, that is meant to identify the terminal to the data processing system to which it is attached, necessarily fixed. This device overcomes these problems when attaching an asynchronous terminal to the IBM System/7 processor via the teleprocessing multiplexor module (TPMM) feature.

Any time the processor is expecting a message from a remote terminal, it must know what the first several bits (preferably 8) of the message will be. These bits are generally predictable and will usually be an address of the remote terminal or an approximate echo of some portion of the message used by the IBM System/7 to poll the remote. A deserializer is inserted in series with the incoming asynchronous bit stream from the terminal via an unclocked modem. The deserializer is preloaded with a known character, which causes a positive compare to take place (necessary for character phase to be established) with an alert decode buffer of the TPMM. The deserializer begins streaming in the known character as soon as bit phase is established from the drop of the start bit and, thereafter, the terminal bit stream flows through the deserializer and is handled in the normal TPMM synchronous receive mode.

As seen in the figure, terminal T is attached via nonclocking modem 1 to the device...