Method and apparatus for limiting the utilization of an asynchronous bus with distributed controlled access
First Claim
1. Bus saturation apparatus for detecting saturation on an asynchronous bus network coupled in common to a plurality of data handling units during the asynchronous transfer of data between different ones of said units during bus cycles of operation granted on a priority basis controlled by a priority network included as part of said bus network, said priority network being distributed to each of said plurality of units, said bus saturation apparatus being included in at least one of said units, said apparatus comprising:
- means coupled to said bus network for monitoring the state of a predetermined one of a number of lines of said bus network indicative of bus activity; and
,bistate indicator means coupled to said monitoring means, said indicator means being set to a predetermined state at a start of a data transfer interval by said one unit and said bistate indicator means being switched to another state by said monitoring means when said monitoring means detects that said bus network is not being saturated.
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Abstract
A plurality of units which are coupled to transfer requests, transfer data over an asynchronous bus network during allocated bus transfer cycles. The network has a tie-breaking bus priority network which is distributed to a common interface portion of each of the plurality of units and grants bus cycles and resolves simultaneous requests on a priority basis. At least one unit includes bus saturation detection apparatus included within its common interface portion for monitoring bus activity over established intervals of time. The detection of the occurrence of at least one available cycle over the given interval of time signals that the bus network is not in a saturated state. When the indicator specifies that the bus network is saturated, the unit throttles down its operation by increasing the amount of time between issuing data requests. Throttling continues until the bus is no longer being saturated.
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Citations
24 Claims
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1. Bus saturation apparatus for detecting saturation on an asynchronous bus network coupled in common to a plurality of data handling units during the asynchronous transfer of data between different ones of said units during bus cycles of operation granted on a priority basis controlled by a priority network included as part of said bus network, said priority network being distributed to each of said plurality of units, said bus saturation apparatus being included in at least one of said units, said apparatus comprising:
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means coupled to said bus network for monitoring the state of a predetermined one of a number of lines of said bus network indicative of bus activity; and
,bistate indicator means coupled to said monitoring means, said indicator means being set to a predetermined state at a start of a data transfer interval by said one unit and said bistate indicator means being switched to another state by said monitoring means when said monitoring means detects that said bus network is not being saturated. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A peripheral controller for controlling the high speed transfer of data from at least one input/output device to and from an asynchronous bus network which connects said controller common with a plurality of data handling units for asynchronously transferring data between different ones of said units during bus cycles of operation granted on a priority basis controlled by a priority network included as part of said bus network, said priority network being distributed to each of said plurality of units, said controller comprising:
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a bus saturation detector coupled to said bus network, said detector including; means coupled to said bus network for monitoring the state of a predetermined one of a number of lines of said bus network indicative of bus activity; and
,a bistable indicator coupled to said monitoring means, said bistable indicator being switched from a first state to a second state by said monitoring means when said monitoring means detects that said bus network is not being saturated; and
,processor means for generating signals for transferring blocks of data between said input/output device and said bus network, said processor means being coupled to said bus saturation detector, said processor means setting said indicator to said first state at a start of a data transfer operation interval and said processor means including means for testing said state of said indicator at a completion of said data transfer operation interval. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
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24. A method of preventing the saturation of an asynchronous bus network coupled in common to a plurality of data handling units in which data is asynchronously transferred between different ones of said units during bus cycles of operation granted on a priority basis controlled by a priority network includes as part of said bus network, said priority network being distributed to each of said plurality of units, said method comprising the steps of:
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including as part of a bus interface of each of a number of said units, a bus saturation detector circuit; monitoring bus cycle activity by connecting an input of said bus saturation detector to a predetermined line of said bus network; setting said detector circuit to a first state at the start of a data transfer by a processor included in said each of a number of units; switching said detector circuit from said first state to a second state when said detector circuit detects an occurrence of an unused bus cycle; testing the state of said detector circuit at the end of said data transfer interval by said processor for determining if said bus network is being saturated; and
,throttling down the rate at which data is being transferred by said processor in a predetermined manner when the state of said detector circuit indicates that said bus network is saturated until said bus network is no longer being saturated.
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Specification