Structure and method for combining PCM and common control data on a backplane bus
First Claim
1. A synchronous communication method for use in a computational unit having access to a synchronous bus and a request/acknowledge line, comprising the steps of:
- providing a queue counter and a count-down counter;
monitoring said request/acknowledge line for packet request signals and packet acknowledge signals asserted on said request/acknowledge line and (i) incrementing a count in said queue counter, whenever a packet request is signalled on said request/acknowledge line and (ii) decrementing said count in said queue counter and a count in said count-down counter, whenever a packet acknowledge signal is asserted on said request/acknowledge line;
asserting on said request/acknowledge line, during one of a first plurality of predetermined time slots, a request to send data, said predetermined time slot being uniquely assigned to said computational unit, and transferring said count in said queue counter to said count-down counter; and
transmitting a data packet on said synchronous bus during a second plurality of predetermined time slots when said count in said count-down counter reaches zero.
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Abstract
A method for transporting common control data on a backplane bus under the SONET standard uses the section and line overhead bytes. A unit is assigned a predefined number of time slots during in the STS-1 synchronous payload envelope to assert a data transmission request on a request/acknowledge bus. Each unit keeps queue and count-down counters for monitoring, respectively, the total number of pending packets in the system and the number of packets ahead of the unit'"'"'s own queued transmission. This method is implemented on a PCM bus using a transmission circuit and a receiving circuit.
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Citations
19 Claims
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1. A synchronous communication method for use in a computational unit having access to a synchronous bus and a request/acknowledge line, comprising the steps of:
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providing a queue counter and a count-down counter; monitoring said request/acknowledge line for packet request signals and packet acknowledge signals asserted on said request/acknowledge line and (i) incrementing a count in said queue counter, whenever a packet request is signalled on said request/acknowledge line and (ii) decrementing said count in said queue counter and a count in said count-down counter, whenever a packet acknowledge signal is asserted on said request/acknowledge line; asserting on said request/acknowledge line, during one of a first plurality of predetermined time slots, a request to send data, said predetermined time slot being uniquely assigned to said computational unit, and transferring said count in said queue counter to said count-down counter; and transmitting a data packet on said synchronous bus during a second plurality of predetermined time slots when said count in said count-down counter reaches zero. - View Dependent Claims (2, 3, 4)
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5. A synchronous communication method for use in a computational unit having access to a synchronous bus and a request/acknowledge line, comprising the steps of:
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providing a queue counter and a count-down counter; monitoring said request/acknowledge line for packet request signals and packet acknowledge signals asserted on said request/acknowledge line and (i) incrementing a count in said queue counter, whenever a packet request is signalled on said request/acknowledge line and (ii) decrementing said count in said queue counter and a count in said count-down counter, whenever a packet acknowledge signal is asserted on said request/acknowledge line; asserting on said request/acknowledge line, during one of a first plurality of predetermined time slots, a request to send data, and transferring said count in said queue counter to said count-down counter; and transmitting a data packet on said synchronous bus during a second plurality of predetermined time slots when said count in said count-down counter reaches zero;
wherein said first plurality of predetermined time slots are allocated from a payload envelope under the SONET standard, and said second plurality of predetermined time slots are allocated from an overhead portion outside of said payload envelope.
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6. A synchronous communication structure for use in a computational unit having access to a synchronous bus and a request/acknowledge line, comprising:
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a queue counter; a count-down counter; means for monitoring said request/acknowledge line for packet request signals and packet acknowledge signals asserted on said request/acknowledge line; means, connected to said means for monitoring, for incrementing a count in said queue counter, whenever a packet request is signalled on said request/acknowledge line; means, connected to said means for monitoring, for decrementing said count in said queue counter and a count in said count-down counter, whenever a packet acknowledge signal is asserted on said request/acknowledge line; means for asserting on said request/acknowledge line, during one of a first plurality of predetermined time slots, a request to send data, said predetermined time slot being uniquely assigned to said computational unit; means, connected to said queue counter and said count-down counter, for transferring said count in said queue counter to said count-down counter; and means, connected to said count-down counter, for transmitting a data packet on said synchronous bus during a second plurality of predetermined time slots when said count in said count-down counter reaches zero. - View Dependent Claims (7, 8, 9)
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10. A system comprising:
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a synchronous bus having a request/acknowledge line; and a plurality of computational units coupled to said synchronous bus, each computational unit having a bus interface circuit comprising; a queue counter; a count-down counter; a monitor for detecting on said request/acknowledge line packet request signals and packet acknowledge signals asserted on said request/acknowledge line; a circuit coupled to said queue counter and said count-down counter for incrementing a count in said queue counter, whenever a packet request is signalled on said request/acknowledge line and for decrementing said count in said queue counter and a count in said count-down counter, whenever a packet acknowledge signal is asserted on said request/acknowledge line; a circuit coupled to said synchronous bus, said queue counter and said count-down counter for asserting on said request/acknowledge line, during one of a first plurality of predetermined time slots, a request to send data, said predetermined time slot being uniquely assigned to said compuational unit, and for transferring said count in said queue counter to said count-down counter; and a circuit coupled to said synchronous bus and said count-down counter for transmitting a data packet on said synchronous bus during a second plurality of predetermined time slots when said count in said count-down counter reaches zero. - View Dependent Claims (11, 12, 13, 14)
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15. A method for use in a system having a synchronous bus with a request/acknowledge line, said method comprising:
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providing a plurality of computational units coupled to said synchronous bus; providing in each of said computational units a queue counter, and a count-down counter; monitoring said synchronous bus to detect on said request/acknowledge line packet request signals and packet acknowledge signals asserted on said request/acknowledge line; incrementing in each computational unit a count in said queue counter, whenever a packet request is signalled on said request/acknowledge line and decrementing in each computational unit said count in said queue counter and a count in said count-down counter, whenever a packet acknowledge signal is asserted on said request/acknowledge line; for each computational unit having a data packet to send, asserting on said request/acknowledge line, during one of a first plurality of predetermined time slots, a request to send data, said predetermined time slot being uniquely assigned to said computational unit and for transferring said count in said queue counter of said computational unit to said count-down counter of said computational unit; and transmitting said data packet on said synchronous bus during a second plurality of predetermined time slots when said count in said count-down counter of said computational unit reaches zero. - View Dependent Claims (16, 17, 18, 19)
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Specification