Priority token protocol circuit for a token ring local area network adaptor
First Claim
1. A fairness protocol circuit for a token ring local area network adaptor having a data-in line for serially carrying tokens/frames, comprising:
- a shift register delay of at least 8 bauds with an input coupled to said data-in line;
a TTT stack coupled to said shift register for serially storing values of old token priority indicators;
an III stack for serially storing values of new token priority indicators;
TTT means coupled to said TTT stack for temporarily storing a last old token "T" placed onto said TTT stack and serially outputting its bits;
stack control means for shifting said III and TTT stacks up or down bit by bit or clearing said stacks in response to a stack control signal;
III means coupled to said III stack for outputting bit by bit the value of a last new token priority indicator "I" stored on said III stack while at the same time maintaining the value of said "I" on said III stack immediately following the outputting and for replacing said "I" with a reservation indicator "R" of the token and discarding said "I";
PvsI comparing means having inputs coupled to a second bit position of said shift register and to said III means and operative to provide outputs if the value of the last new token priority indicator "I" is less than or greater than the value of the token priority indicator "P";
RGTP comparing means having inputs coupled to said shift register first and sixth bit positions and operative to provide an output if the value of the token reservation "R" is greater than the token priority indicator "P";
RGTT comparing means having inputs coupled to said shift register first bit position and to said TTT means and operative to provide an output if the value of the token reservation "R" is greater than the value of the last old token priority indicator "T";
an input selector inputs of which are coupled to an output of said shift register, to said TTT means to the fourth bit position of said shift register and a select control signal which transmits a selected one of said input selector inputs to its output in response to the select control signal applied thereto; and
a state machine having inputs coupled to outputs of said PvsI, RGTP, RGTT comparing means and to said IEQZ output from said III stack and operative in response to selected combinations of its inputs to issue control signals to said stacks, said III means, said TTT means, and to said PvsI, RGTP, RGTT comparing means.
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Accused Products
Abstract
A fairness protocol circuit for a token ring local area network adaptor having a data-in line for serially carrying tokens/frames and a shift register delay of at least 18 bauds with an input coupled to the data-in line. A TTT stack is coupled to the shift register delay for serially storing values of old token indicators. An III stack is provided for serially storing values of new token priority indicators. TTT means is coupled to the TTT stack for temporarily storing a last old token placed on the TTT stack and serially outputting its bits. The stacks shift up or down bit by bit in response to UNSTACK or STACK control signals and are cleared in response to a clear signal. III means is coupled to the III stack for outputting bit by bit the value of a last new token priority idicator "I" stored on the III stack while at the same time maintaining the value of the last new token priority indicator on the III stack immediately following the outputtting and for replacing the last new token priority indicator stored with a reservation indicator "R" of the token and discarding the last new token priority indicator. Means are provided for comparing "P" and "I", "R" and "P" and "R" and "T". An output data modifier has inputs coupled to an output of the shift register delay, the TTT means, to a selected bit position of the shift delay and transmits a selected one of the inputs to the output in response to selected control signals applied thereto. Finally, a fairness state machine having inputs coupled to outputs of the comparing means and to an IEQZ output of the III stack is operative in response to selected combinations of its inputs to issue control signals to the stacks, the III means, the TTT means and the comparing means.
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Citations
22 Claims
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1. A fairness protocol circuit for a token ring local area network adaptor having a data-in line for serially carrying tokens/frames, comprising:
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a shift register delay of at least 8 bauds with an input coupled to said data-in line; a TTT stack coupled to said shift register for serially storing values of old token priority indicators; an III stack for serially storing values of new token priority indicators; TTT means coupled to said TTT stack for temporarily storing a last old token "T" placed onto said TTT stack and serially outputting its bits; stack control means for shifting said III and TTT stacks up or down bit by bit or clearing said stacks in response to a stack control signal; III means coupled to said III stack for outputting bit by bit the value of a last new token priority indicator "I" stored on said III stack while at the same time maintaining the value of said "I" on said III stack immediately following the outputting and for replacing said "I" with a reservation indicator "R" of the token and discarding said "I"; PvsI comparing means having inputs coupled to a second bit position of said shift register and to said III means and operative to provide outputs if the value of the last new token priority indicator "I" is less than or greater than the value of the token priority indicator "P"; RGTP comparing means having inputs coupled to said shift register first and sixth bit positions and operative to provide an output if the value of the token reservation "R" is greater than the token priority indicator "P"; RGTT comparing means having inputs coupled to said shift register first bit position and to said TTT means and operative to provide an output if the value of the token reservation "R" is greater than the value of the last old token priority indicator "T"; an input selector inputs of which are coupled to an output of said shift register, to said TTT means to the fourth bit position of said shift register and a select control signal which transmits a selected one of said input selector inputs to its output in response to the select control signal applied thereto; and a state machine having inputs coupled to outputs of said PvsI, RGTP, RGTT comparing means and to said IEQZ output from said III stack and operative in response to selected combinations of its inputs to issue control signals to said stacks, said III means, said TTT means, and to said PvsI, RGTP, RGTT comparing means. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A fairness protocol circuit for a token ring local area network adaptor having a data-in line for serially carrying tokens/frames, comprising:
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a shift register delay of at least 8 bauds coupled to said data-in line; a serial bidirectional shift register TTT stack coupled to said shift register delay for serially storing values of old token priority indicators; a serial bidirectional shift register III stack for storing values of old token priority indicators; a 3 baud TTT shift register coupled to said TTT stack so that a parallel transfer of data in the top 3 baud positions of said TTT stack can be made to said TTT shift register in response to a LOADIT control signal and so a serial shift of data out of said TTT register is in continuous progress except when transferring data from said TTT stack; III retention means coupled to said III stack for outputting bit by bit the value of a last new token priority indicator "I" stored on said III stack while at the same time maintaining the value of said "I" on said III stack immediately following the outputting and for replacing said "I" with a reservation indicator "R" of the token and discarding said "I"; a PvsI comparator having inputs coupled to a second baud position of said shift register and to said III retention means and operative to provide outputs if the value of the last new token priority indicator "I" is less than or greater than the value of the token priority indicator "P"; an RGTP comparator having inputs coupled to said shift register first and sixth bit positions and operative to provide an output if the value of the token reservation "R" is greater than the token priority indicator "P"; an RGTT comparator having inputs coupled to said shift register delay first baud position and to said TTT means and operative to provide an output if the value of the token reservation "R" is greater than the value of the last old token priority indicator "T"; an output multiplexer having a first input coupled to an output of said shift register, a second input coupled to an output of said TTT retention means and a third input coupled to a fourth baud position of said shift register delay and operative to transmit a selected one of its inputs to its output in response to control signals applied thereto; and a state machine having inputs coupled to outputs of said Pvs I, RGTP, RGTT comparators and to an IEQZ output from said III stack and operative in respone to selected combinations of its inputs to issue control signals to said stacks, said III means, said TTT means, and to said PvsI, RGTP, RGTT comparators. - View Dependent Claims (10, 11)
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12. A method of controlling fairness protocol on a token ring local area network system on which circulate from station to station tokens and frames having an access priority field which includes a 3 bit priority field, a token indicator bit, a monitor count bit and a 3 bit priority reservation field, comprising:
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detecting the arrival of an incoming or internally generated token/frame; comparing the priority indicator "P" of a token/frame arriving at a given station with a new priority indicator "I" of the last token whose priority was modified by that station; comparing the value of the reservation of the token/frame "R" with the value of the old priority indicator "T" of the last token whose priority was modified by that station; comparing the value of "R" to that of "P"; replacing "P" of the token/frame by "R" if "R" is greater than "P" and storing the value of "R" as "I" and the value of "P" as "T" and clearing the "R" and monitor count of the outgoing token/frame; replacing the priority indicator "P" of the token by the value of "T" if "P" equals "I" and discarding the last stored values of "I" and "T" and clearing the monitor count; replacing "P" of the token by "R" if "P" equals "I" and "R" is greater than "T" and substituting "R" for the last stored "I" value and clearing the reservation and monitor count of the token; discarding the values of "I" and "T" if "P" is less than "I"; removing fairness from being active if the value of "I" "T" and Rare Zero. - View Dependent Claims (13, 14, 15, 16, 17, 18)
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19. A local area network system, comprising:
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a token/frame conducting ring; a plurality of host stations; and a plurality of adaptors coupled between said ring and respective host stations for interfacing associated host stations to said ring, wherein each adaptor has a token/frame priority protocol circuit for reading priority protocol values of circulating tokens/frames, and in response to a comparison of such values with priority values stored therein, either re-transmitting such tokens/frames or copying such tokens/frames and generating and transmitting new tokens/frames onto said ring; wherein said token or frame priority protocol circuit includes; means for detecting the arrival of an incoming or internally generated token or frame; means for comparing a priority indicator "P" of an arriving token/frame at a given station with a new priority indicator "I" of the last token whose priority was modified by that station; means for comparing a reservation value "R" of a token/frame with the value of an old priority indicator "T" of the last token whose priority was modified by that station; means for comparing the value of "R" to the value of "P"; means for replacing "P" of the token/frame by "R" if "R" is greater than "P" and storing the value of "R" as "I" and the value of "P" as "T" and clearing the "R" and monitor count of the outgoing token/frame; means for replacing "P" of the token by the value of "T" if "P" equals "I" and discarding the last stored values of "I" and "T" and clearing the monitor count; means for replacing "P" of the token by "R" if "P" equals "I" and "R" is greater than "T" and substituting "R" for the last stored "I" value and clearing the reservation and monitor count of the token; discarding the values of "I" and "T" if "P" is less than "I"; and means for inactivating fairness when the values of "I" and "T" are zero and "R"=0. - View Dependent Claims (20, 21, 22)
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Specification