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EP0341711A2
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EP
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Fair arbitration scheme
Assignee: Digital Equipment Corp
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Filing: 1989-05-11
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Granted: —
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Expires: 2009-05-11
Abstract
Abstract A method and apparatus for selecting a particular node from a plurality of nodes connected to a common bus to allow the node to use the bus. The nodes have a predetermined priority. After initially enabling the nodes, the bus is monitored for a bus idle condition. It is then determined which of the nodes are enabled message nodes, which are enabled nodes that have a message to send on the bus. There is then arbitration between the enabled message nodes after the bus is in the bus idle condition for a first period of time, such that the enabled message node having the highest pre-determined priority among the enabled message nodes is disabled for arbitration purposes, and also at the same time selects a target and performs a transfer. This procedure is repeated until all the enabled message nodes have been disabled. Thereafter, all of the nodes on the bus are enabled when the bus is in the bus idle condition for a second period of time, which is longer than the first period of time.
Inventors
- 👤 Robert C. Frame
- 👤 Fernando A. Zayas
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-26 06:34
CPC Classifications
G; G06; G06F; G06F13/00; G06F13/14; G06F13/36; G06F13/368
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
176 words
A method for selecting a particular node from a plurality of nodes connected to a common bus to allow said node to use said bus, said method comprising the steps of: a. enabling said nodes, each said node having a pre-determined priority; b. monitoring the bus for a bus idle condition; c. determining which of said nodes are enabled message nodes, said enabled message nodes being enabled nodes that have a message to send on said bus; d. arbitrating between said enabled message nodes after the bus is in said bus idle condition for a first period of time, such that said enabled message node having a highest predetermined priority among said enabled message nodes is selected to use the bus; e. disabling said selected enabled message node; f. repeating steps b, c, d and e until all said enabled message nodes have been disabled; and g. thereafter enabling all said nodes when the bus is in said bus idle condition for a second period of time which is longer than said first period of time.
Claim 2
Independent Claim
176 words
A method for selecting a particular node from a plurality of nodes connected to a common bus to allow said node to use said bus, said method comprising the steps of: a. enabling said nodes, each said node having a pre-determined priority; b. monitoring the bus for a bus idle condition; c. determining which of said nodes are enabled message nodes, said enabled message nodes being enabled nodes that have a message to send on said bus; d. arbitrating between said enabled message nodes after the bus is in said bus idle condition for a first period of time, such that said enabled message node having a highest predetermined priority among said enabled message nodes is selected to use the bus; e. disabling said selected enabled message node; f. repeating steps b, c, d and e until all said enabled message nodes have been disabled; and g. thereafter enabling all said nodes when the bus is in said bus idle condition for a second period of time which is longer than said first period of time.
Claim 3
Dependent Claim
25 words
The method of claim 1, further comprising the step of monitoring the period of time elapsed after said bus enters into said bus idle condition.
Claim 4
Dependent Claim
21 words
The method of claim 2, wherein step (a) includes the step of setting an internal enable flag in each said node.
Claim 5
Dependent Claim
23 words
The method of claim 3, wherein step (e) includes the step of clearing said internal enable flag of said selected enabled message node.
Claim 6
Dependent Claim
30 words
The method of claim 4, wherein step (c) includes determining which of said enabled nodes have asserted a busy signal which indicates said enabled node has a message to send.
Claim 7
Dependent Claim
31 words
The method of claim 5, wherein step (d) includes comparing a priority asserted by each said enabled message node, and selecting said enabled message node which has asserted a highest priority.
Claim 8
Dependent Claim
21 words
The method of claim 1, wherein step (a) includes the step of setting an internal enable flag in each said node.
Claim 9
Dependent Claim
23 words
The method of claim 7, wherein step (e) includes the step of clearing said internal enable flag of said selected enabled message node.
Claim 10
Dependent Claim
30 words
The method of claim 1, wherein step (c) includes determining which of said enabled nodes have asserted a busy signal which indicates said enabled node has a message to send.
Claim 11
Dependent Claim
33 words
The method of claim 1, wherein step (d) includes comparing a priority identification bit asserted by each said enabled message node, and selecting said enabled message node which has asserted a highest priority.
Claim 12
Dependent Claim
25 words
The method of claim 1, wherein said first period of time is approximately 800 nsec, and said second period of time is approximately 1600 nsec.
Claim 13
Dependent Claim
172 words
A fair arbitration device for selecting a particular node from a plurality of nodes coupled to a common bus to allow said node to use said bus, said device comprising: means for enabling said nodes, each said node having a pre-determined priority; means for monitoring the bus to detect a bus idle condition and for measuring an amount of time elapsed after said bus enters into said bus idle condition; means for arbitrating and selecting between said enabled message nodes after the bus is in said bus idle condition for a first period of time, such that said enabled message node having a highest pre-determined priority among said enabled message nodes is selected to use the bus; means for disabling the selected enabled message node until all enabled message nodes have been disabled; wherein said monitoring and measuring means causes said enabling means to enable all said nodes when the bus is in said bus idle condition for a second period of time which is longer than said first period of time.
Claim 14
Dependent Claim
172 words
A fair arbitration device for selecting a particular node from a plurality of nodes coupled to a common bus to allow said node to use said bus, said device comprising: means for enabling said nodes, each said node having a pre-determined priority; means for monitoring the bus to detect a bus idle condition and for measuring an amount of time elapsed after said bus enters into said bus idle condition; means for arbitrating and selecting between said enabled message nodes after the bus is in said bus idle condition for a first period of time, such that said enabled message node having a highest pre-determined priority among said enabled message nodes is selected to use the bus; means for disabling the selected enabled message node until all enabled message nodes have been disabled; wherein said monitoring and measuring means causes said enabling means to enable all said nodes when the bus is in said bus idle condition for a second period of time which is longer than said first period of time.
Claim 15
Dependent Claim
175 words
A node adapted to be coupled to a bus with at least one other node, the node comprising: means for enabling said node such that said node becomes an enabled message node, said node having a pre-determined priority; means for monitoring the bus to detect a bus idle condition and for measuring an amount of time elapsed after said bus enters into said bus idle condition; means for arbitrating and selecting between enabled message nodes coupled to said bus after the bus is in said bus idle condition for a first period of time, such that said enabled message node having a highest pre-determined priority among said enabled message nodes is selected to use the bus; means for disabling the selected enabled message node until all enabled message nodes have been disabled; wherein said monitoring and measuring means causes said enabling means to enable all said nodes coupled to said bus when the bus is in said bus idle condition for a second period of time which is longer than said first period of time.
Claim 16
Dependent Claim
175 words
A node adapted to be coupled to a bus with at least one other node, the node comprising: means for enabling said node such that said node becomes an enabled message node, said node having a pre-determined priority; means for monitoring the bus to detect a bus idle condition and for measuring an amount of time elapsed after said bus enters into said bus idle condition; means for arbitrating and selecting between enabled message nodes coupled to said bus after the bus is in said bus idle condition for a first period of time, such that said enabled message node having a highest pre-determined priority among said enabled message nodes is selected to use the bus; means for disabling the selected enabled message node until all enabled message nodes have been disabled; wherein said monitoring and measuring means causes said enabling means to enable all said nodes coupled to said bus when the bus is in said bus idle condition for a second period of time which is longer than said first period of time.
Claim 17
Dependent Claim
165 words
A computer system comprising: a bus; a plurality of nodes coupled to the bus; means for enabling said nodes such that said node becomes an enabled message node, each said node having a pre-determined priority; means for monitoring the bus to detect a bus idle condition and for measuring an amount of time elapsed after said bus enters into said bus idle condition; means for arbitrating and selecting between said enabled message nodes after the bus is in said bus idle condition for a first period of time, such that said enabled message node having a highest pre-determined priority among said enabled message nodes is selected to use the bus; means for disabling the selected enabled message node until all enabled message nodes have been disabled; wherein said monitoring and measuring means causes said enabling means to enable all said nodes when the bus is in said bus idle condition for a second period of time which is longer than said first period of time.
Claim 18
Dependent Claim
165 words
A computer system comprising: a bus; a plurality of nodes coupled to the bus; means for enabling said nodes such that said node becomes an enabled message node, each said node having a pre-determined priority; means for monitoring the bus to detect a bus idle condition and for measuring an amount of time elapsed after said bus enters into said bus idle condition; means for arbitrating and selecting between said enabled message nodes after the bus is in said bus idle condition for a first period of time, such that said enabled message node having a highest pre-determined priority among said enabled message nodes is selected to use the bus; means for disabling the selected enabled message node until all enabled message nodes have been disabled; wherein said monitoring and measuring means causes said enabling means to enable all said nodes when the bus is in said bus idle condition for a second period of time which is longer than said first period of time.
References Cited (Backward Citations)
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