Dismiss
InnovationQ will be updated on Sunday, Oct. 22, from 10am ET - noon. You may experience brief service interruptions during that time.
Browse Prior Art Database

Time Division Multiplexed Service Requesting

IP.com Disclosure Number: IPCOM000100884D
Original Publication Date: 1990-Jun-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 7 page(s) / 248K

Publishing Venue

IBM

Related People

Bourke, DG: AUTHOR [+3]

Abstract

A technique is described whereby bus-interconnected processing units are provided with time division multiplexed (TDM) service requesting. Comparisons are made with three existing requesting and servicing techniques (time division, serial and radial) to show that TDM pro vides all of the advantages of the three requesting techniques and, in addition, significantly reduces the line count in the service provider in the case of radial servicing.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 30% of the total text.

Time Division Multiplexed Service Requesting

       A technique is described whereby bus-interconnected
processing units are provided with time division multiplexed (TDM)
service requesting.  Comparisons are made with three existing
requesting and servicing techniques (time division, serial and
radial) to show that TDM pro vides all of the advantages of the three
requesting techniques and, in addition, significantly reduces the
line count in the service provider in the case of radial servicing.

      TDM service requesting provides bus service from a bus arbiter,
where the service is a grant from the arbiter to use the bus or
interrupt service from a processor, and the service is an
acknowledgement and capture of the interrupted data by means of the
bus.  It is adaptable to bus arbitration and interrupt
acknowledgement techniques and overcomes most of the disadvantages
seen in serial methods of service requesting. Primarily, TDM reduces
the number of signal lines previously required by radial techniques.
Requesting is overlapped with the bus data operations, and request
latencies are normal.  Grant/ acknowledgement capability is
immediate, not time division multiplexed, and, therefore, has no
intrinsic latency. Granting, or acknowledgement, is done on the basis
of bus bandwidth available for the requested demand, as with
conventional "service on demand" techniques.

      The block diagram of Fig. 1 illustrates the use of TDM service
requesting and is not unlike conventional techniques, except that the
request on each priority level is a TDM function on its appropriate
request line.  The diagram shows that up to K bus units would be
attached to a bus and that the lines necessary for priority
requesting to a service provider would be up to P levels, as well as
the granting of service to one particular requester.

      Time division multiplexing of request lines is based on a fixed
assignment of time slots, which are based on a bus unit address
(BUA).  The BUA is imparted uniquely to the bus units by a wired
binary signature from the backplane, with each value of the signature
unique to each bus unit slot. The BUA is therefore a physical address
of the unit's location on the backplane.  Although the technique of
imparting physical addresses to bus units from the backplane is well
known, the technique of using physical address signatures to assign
time slots to TDM bus unit requests is unique to the concept
described herein.

      Each bus unit and the service provider has an address counter,
as shown in Fig. 2, of modulus K*n, where K is the maximum number of
bus units that the bus is designed to be attached and n is the number
of time slots a bus unit needs to post a request, have the service
provider recognize it, and clear the bus for the next requester.  The
address counters are clocked at a frequency which is, by definition,
the time slot frequency.  They receive first-order clocking (time
slot frequency) f...