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Serial Channel Extender Link With SELECT in and SELECT OUT Control Lines Configured for Assigning a Selected PRIORITY Sequence Position to the Serial Link

IP.com Disclosure Number: IPCOM000039379D
Original Publication Date: 1987-May-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 3 page(s) / 71K

Publishing Venue

IBM

Related People

Fredericks, KJ: AUTHOR [+2]

Abstract

A serial channel extender has a bidirectional serial link and a component at one end of the link called the X box and a component at the other end of the link called the Y box. The X box is connected to the parallel bus like a control unit, and several conventional control units can also be connected to this part of the parallel bus. An extension of the parallel bus is connected to the Y box, and several control units are connected to the box extension. See IBM Technical Disclosure Bulletin 19, 3139-3143 (January 1977). The conventional parallel bus includes a pair of lines called Select Out and Select In that are connected to the control units in a (Image Omitted) way that establishes a priority sequence among the control units.

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Serial Channel Extender Link With SELECT in and SELECT OUT Control Lines Configured for Assigning a Selected PRIORITY Sequence Position to the Serial Link

A serial channel extender has a bidirectional serial link and a component at one end of the link called the X box and a component at the other end of the link called the Y box. The X box is connected to the parallel bus like a control unit, and several conventional control units can also be connected to this part of the parallel bus.

An extension of the parallel bus is connected to the Y box, and several control units are connected to the box extension. See IBM Technical Disclosure Bulletin 19, 3139-3143 (January 1977). The conventional parallel bus includes a pair of lines called Select Out and Select In that are connected to the control units in a

(Image Omitted)

way that establishes a priority sequence among the control units. Logically, Select Out and Select In make a loop through each control unit, and on a general poll the signal Select Out is propagated from one control unit to the next until one control unit blocks further propagation and then begins a procedure to acquire control of the other lines of the parallel bus.

Physically, Select Out and Select In are constructed as a bus of two conductors that are joined at the end remote from the channel. The two-conductor bus passes into and out of each control unit, and inside a control unit the priority circuits are connected in series with the incoming and outgoing parts of one of the lines, and jumpers are connected in series with the incoming and outgoing parts of the other line. Since the selection signal is propagated first along Select Out and then along Select In, a control unit can be assigned a relatively high priority by connecting its priority circuits in series with Select Out and it can be given a relatively low priority by connecting its priority circuits in series with Select In. Select Out and Select...