Systems for implementing SDRAM controllers, and buses adapted to include advanced high performance bus features
View Patent ↗An arbitration logic including one or more modular priority encoders. Each modular priority encoder includes a first logic circuit, a comparator circuit, a second logic circuit, and an encoder circuit. The first logic circuit may be configured to generate a first output signal in response to a plurality of request signals. The comparator circuit may be configured to compare all possible pairs of a plurality of priority signals. The second logic circuit may be configured to generate a control signal in response to (i) the plurality of request signals and (ii) a result of comparing all possible pairs of the plurality of priority signals. The encoder circuit may be configured to generate a second output signal in response to the control signal.
1. An arbitration logic including one or more modular priority encoders, each modular priority encoder comprising:
a first logic circuit configured to generate a first output signal in response to a plurality of request signals;
a comparator circuit configured to compare all possible pairs of a plurality of priority signals, wherein the comparator circuit is configured to receive the plurality of priority signals and generate a comparison signal representing the result of comparing all possible pairs of the plurality of priority signals;
a second logic circuit configured to generate a control signal in response to (i) the plurality of request signals and (ii) the result of comparing all possible pairs of the plurality of priority signals;
an encoder circuit configured to generate a second output signal in response to the control signal; and
a third logic circuit configured to generate a third output signal and a fourth output signal in response to the control signal, the plurality of priority signals, and a plurality of input signals.
2. The arbitration logic according to claim 1 , wherein said third logic circuit comprises:
a first multiplexer circuit configured to generate the third output signal in response to the control signal and the plurality of input signals; and
a second multiplexer circuit configured to generate the fourth output signal in response to the control signal and the plurality of priority signals.
3. The arbitration logic according to claim 1 , wherein the plurality of request signals comprises three or more request signals, the plurality of priority signals comprises three or more priority signals and a plurality of the modular priority encoders are coupled as levels of a tree.
4. The arbitration logic according to claim 1 , wherein the comparator circuit is biased to implement a tie breaking scheme.
5. The arbitration logic according to claim 4 , wherein the comparator circuit is configured such that masters with lower numbers win ties.
6. The arbitration logic according to claim 1 , wherein:
the order in which pairs of priority signals are compared is fixed.
7. The arbitration logic according to claim 1 , wherein the first logic circuit is configured to assert the first output signal in response to any of the plurality of request signals being asserted.
8. A method of arbitration comprising:
generating a first output signal in response to a plurality of request signals;
receiving a plurality of priority signals;
generating a comparison signal representing a result of comparing all possible pairs of the plurality of priority signals;
generating a control signal in response to (i) the plurality of request signals and (ii) the result of comparing all possible pairs of the plurality of priority signals;
generating a second output signal in response to the control signal; and
generating a third output signal and a fourth output signal in response to the control signal, the plurality of priority signals, and a plurality of input signals.
9. The method according to claim 8 , wherein generating said third output signal comprises selecting one of the plurality of input signals for presentation as said third output signal in response to said control signal.
10. The method according to claim 8 , wherein generating said fourth output signal comprises selecting one of the plurality of priority signals for presentation as said fourth output signal in response to said control signal.
11. The method according to claim 8 , wherein the plurality of request signals comprises three or more request signals, the plurality of priority signals comprises three or more priority signals and said arbitration is performed using a plurality of modular priority encoders coupled as levels of a tree.
12. The method according to claim 8 , wherein the step of comparing all possible pairs of the plurality of priority signals comprises breaking ties between masters having similar priorities.
13. The method according to claim 12 , wherein breaking ties between masters having similar priorities comprises assigning numbers to the masters and giving priority to the master having a lower number.
14. A memory controller configured to couple an Advanced High Performance Bus (AHB) and a synchronous dynamic random access memory (SDRAM), the memory controller comprising:
a write data path;
a read data path; and
an arbitration logic circuit configured to handle Advanced High Performance Bus (AHB) busy transactions without using buffers or queues, said arbitration logic circuit including one or more modular priority encoders, each modular priority encoder comprising
(a) a first logic circuit configured to generate a first output signal in response to a plurality of request signals,
(b) a comparator circuit configured to compare all possible pairs of a plurality of priority signals, wherein the comparator circuit is configured to receive the plurality of priority signals and generate a comparison signal representing the result of comparing all possible pairs of the plurality of priority signals,
(c) a second logic circuit configured to generate a control signal in response to (i) the plurality of request signals and (ii) the result of comparing all possible pairs of the plurality of priority signals,
(d) an encoder circuit configured to generate a second output signal in response to the control signal, and
(e) a third logic circuit configured to generate a third output signal and a fourth output signal in response to the control signal, the plurality of priority signals, and a plurality of input signals.
15. The memory controller according to claim 14 , wherein said arbitration logic circuit is configured to handle Advanced High Performance Bus (AHB) busy transactions using a clock enable input of the memory to suspend a flow of data.
16. The memory controller according to claim 14 , wherein said arbitration logic circuit is configured to handle Advanced High Performance Bus (AHB) busy transactions using a delayed write busy signal to inhibit a column address strobe (CAS).
17. The memory controller according to claim 14 , wherein said arbitration logic circuit is configured to handle Advanced High Performance Bus (AHB) busy transactions using a read busy signal to inhibit the column address strobe (CAS).
18. The memory controller according to claim 14 , wherein said arbitration logic circuit is configured to handle Advanced High Performance Bus (AHB) busy transactions using the read busy signal and a delayed version of the read busy signal to control loading of registers in the read data path.