Browse Prior Art Database

Point To Point Communication Adapter

IP.com Disclosure Number: IPCOM000087099D
Original Publication Date: 1976-Dec-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 33K

Publishing Venue

IBM

Related People

Bosch, LJ: AUTHOR

Abstract

Multiplexing between a primary terminal and many secondary terminals is accomplished without software intervention and with the use of minimum hardware. A counter whose count represents an addressed secondary terminal (port) is stepped to interrogate sequentially a plurality of latches whose stored data represents whether or not respective ports are to be serviced and, if so, the nature of the required service. The count in the counter also is used to select the secondary terminals and to select a memory buffer area for each secondary terminal.

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Point To Point Communication Adapter

Multiplexing between a primary terminal and many secondary terminals is accomplished without software intervention and with the use of minimum hardware. A counter whose count represents an addressed secondary terminal (port) is stepped to interrogate sequentially a plurality of latches whose stored data represents whether or not respective ports are to be serviced and, if so, the nature of the required service. The count in the counter also is used to select the secondary terminals and to select a memory buffer area for each secondary terminal.

Referring to the figure, port counter 1 is stepped through sequential count values, each value representing a respective port. The count is decoded to energize selectively an appropriate one of the output lines 2 which address respective latches comprising port mask register 3. Register 3 previously was loaded with mask data, each set of data representing whether a respective port has requested service as well as the nature of the requested service (poll, write, step, etc.). The "step" code is loaded into a given storage area of register 3, if a corresponding port requests no service or if a requested service has been completed. The sensing of a "step" code in a given storage area causes the application of a "step" signal to be applied to counter 1 via line 6.

The count in port counter 1 also is decoded (4) to select the port to be communicated and is applied to control word register 5...