Double data rate (DDR) memory controller apparatus and method
A computer-implemented method includes an act of configuring hardware to cause at least a part of the hardware to operate as a double data rate (DDR) memory controller, and to produce a capture clock to time a read data path, where a timing of the capture clock is based on a first clock signal of a first clock, delay the first clock signal to produce a delayed first clock signal, adjust the delay such that at least one clock edge of the delayed first clock signal is placed nearer to at least one clock edge of at least one data strobe (DQS), or at least one signal dependent on a DQS timing, and produce a modified timing of the capture clock based on the delay of the first clock signal.
1. A computer-implemented method, comprising an act of:
configuring hardware to cause at least a part of the hardware to operate as a double data rate (DDR) memory controller, and to:
produce a capture clock to time a read data path, where a timing of the capture clock is based on a first clock signal of a first clock;
delay the first clock signal to produce a delayed first clock signal;
adjust the delay such that at least one clock edge of the delayed first clock signal is placed nearer to at least one clock edge of:
at least one data strobe (DQS); or
at least one signal dependent on a DQS timing; and
produce a modified timing of the capture clock based on the delay of the first clock signal.
2. The method of claim 1 , and comprising an additional act of further configuring the hardware to cause the at least part of the hardware to operate such that the first clock signal is a core clock signal or a signal derived from at least the core clock signal.
3. The method of claim 1 , and comprising an additional act of further configuring the hardware to cause the at least part of the hardware to issue a sequence of read commands so that at least one of:
the at least one DQS toggles repeatedly; or
the at least one signal dependent on the DQS timing toggles repeatedly.
4. The method of claim 1 , and comprising an additional act of further configuring the hardware to cause the at least part of the hardware to operate such that the adjusting the delay produces a plurality of the clock edges of the delayed first clock signal that are a function of the least one clock edge.
5. The method of claim 1 , and comprising an additional act of further configuring the hardware to cause the at least part of the hardware to operate such that the at least one clock edge includes the at least one clock edge of the at least one signal dependent on the DQS timing, and the at least one clock edge is a delayed version of another at least one DQS.
6. The method of claim 1 , and comprising an additional act of further configuring the hardware to cause the at least part of the hardware to adjust the timing of the capture clock by monitoring the DQS timing or a signal dependent on the DQS timing.
7. The method of claim 1 , and comprising an additional act of further configuring the hardware to cause the at least part of the hardware to produce the capture clock such that the capture clock runs at a same clock frequency as a memory clock of a memory.
8. The method of claim 1 , and comprising an additional act of further configuring the hardware to cause the at least part of the hardware to produce the capture clock such that the capture clock at a clock frequency that is the same as, a multiple of, or a sub-multiple of a frequency of read data in the read data path.
9. The method of claim 1 , and comprising an additional act of further configuring the hardware to cause the at least part of the hardware to use a calibration sequence to place the capture clock in a more optimum sampling position in a read data eye.
10. The method of claim 1 , and comprising an additional act of further configuring the hardware to cause the at least part of the hardware to operate such that the capture clock is adjusted to place capture of read data closer to a middle of a data eye.
11. The method of claim 1 , and comprising an additional act of further configuring the hardware to cause the at least part of the hardware to operate such that read data is captured directly in one or more registers.
12. The method of claim 1 , and comprising an additional act of further configuring the hardware to cause the at least part of the hardware to operate such that read data is directly captured from memory.
13. The method of claim 1 , and comprising an additional act of further configuring the hardware to cause the at least part of the hardware to operate such that the capture clock is adjusted to increase a reliability of a capture of read data from a memory.
14. The method of claim 1 , and comprising an additional act of further configuring the hardware to cause the at least part of the hardware to operate such that a read timing training calibration sequence is performed to increase a reliability of a capture of read data from a memory.
15. The method of claim 14 , and comprising an additional act of further configuring the hardware to cause the at least part of the hardware to operate such that at least one delay element is adjusted during the read timing training calibration sequence.
16. The method of claim 15 , and comprising an additional act of further configuring the hardware to cause the at least part of the hardware to operate such that the adjustment of the at least one delay element causes an adjustment of a phase of the capture clock.
17. The method of claim 1 , and comprising an additional act of further configuring the hardware to cause the at least part of the hardware to operate such that the capture clock is produced by a capture clock generation circuit.
18. The method of claim 17 , and comprising an additional act of further configuring the hardware to cause the at least part of the hardware to operate such that the capture clock generation circuit adjusts a timing of the capture clock to match a phase of a memory clock of a memory.
19. The method of claim 1 , and comprising an additional act of further configuring the hardware to cause the at least part of the hardware to operate such that the modified timing of the capture clock accommodates at least one of a variation of voltage or a variation of temperature.
20. The method of claim 19 , and comprising an additional act of further configuring the hardware to cause the at least part of the hardware to operate such that the accommodation is performed by at least one of a capture clock generation circuit or a circuit driving a capture clock generation circuit.