Memory link training
View Patent ↗An apparatus and method are disclosed. In one embodiment, the apparatus trains a memory link using a signal alignment unit. The signal alignment unit aligns a read data strobe signal that is transmitted on the link with the center of a read data eye transmitted on the link. Next, the signal alignment unit aligns a receive enable signal that is transmitted on the link with the absolute time that data returns the data lines of the link a column address strobe signal is sent to the memory coupled to the link. Next, the signal alignment unit aligns a write data strobe signal transmitted on the link with the link's clock signal. Finally, the signal alignment unit aligns the center of the write data eye transmitted on the link with the write data strobe transmitted on the link.
1. An apparatus to train a memory link, comprising:
a signal alignment unit, coupled to a plurality of signal lines of the link, operable to
align a read data strobe signal of the link on a center of a read data eye of the link;
align a receive enable signal of the link with a time that data returns on one or more data lines of the link after a column address strobe signal is sent to a memory coupled to the link;
align a write data strobe signal of the link with a clock signal of the link; and
align a center of a write data eye of the link with a write data strobe of the Link;
an alignment timeout timer to time out of one or more of the align operations if one or more of the align operations takes longer than a predetermined maximum time designated for an align operation; and
an alignment error register to store one or more alignment error flags, each alignment error flag being designated to report an alignment error for one of the one or more align operations, wherein an alignment error flag is set if the time spent on its designated align operation exceeds the predetermined maximum time.
2. The apparatus of claim 1 , wherein the signal alignment unit further comprises a plurality of delay locked loops, each one of the plurality of delay locked loops being pairingly coupled to one of the plurality of signal lines.
3. The apparatus of claim 2 , wherein the signal alignment unit is further operable to
select a reference signal line; and
shift a first signal phase transmitted on a first signal line of the plurality of signal lines, utilizing the delay locked loop pairingly coupled to the first signal line, relative to a phase of a reference signal transmitted on the reference signal line to align the first signal phase with the reference signal phase.
4. The apparatus of claim 1 , wherein the signal alignment unit is further operable to align the receive enable signal, the read data strobe signal, the write data strobe signal, and the center of the write data eye for each of a plurality of ranks in the memory.
5. The apparatus of claim 1 , wherein the signal alignment unit further comprises an alignment complete flag, wherein the signal alignment unit sets the alignment complete flag when all signal alignment operations are complete and no error flags are set in the alignment error register.
6. The apparatus of claim 1 , wherein the signal alignment unit performs one or more of the signal alignments in response to a setting in a basic input/output system (BIOS) to align a signal.
7. The apparatus of claim 1 , wherein the signal alignment unit performs one or more of the signal alignments dynamically in response to a system event.
8. A method of training a memory link, comprising:
aligning a read data strobe signal of the link on a center of a read data eye of the link;
aligning a receive enable signal of the link, the link being comprised of a plurality of signal lines, with a time that data returns on one or more data lines of the link after a column address strobe signal is sent to a memory coupled to the link;
aligning a write data strobe signal of the link with a clock signal of the link;
aligning a center of a write data eye of the link with a write data strobe of the link;
timing out of one or more of the align operations if one or more of the align operations takes longer than a predetermined maximum time designated for an align operation; and
storing one or more alignment error flags, each alignment error flag being designated to report an alignment error for one of the one or more align operations, wherein an alignment error flag is set if the time spent on its designated align operation exceeds the predetermined maximum time.
9. The method of claim 8 , further comprising:
selecting a reference signal line; and
shifting a first signal phase transmitted on a first signal line of the plurality of signal lines relative to a phase of a reference signal transmitted on the reference signal line to align the first signal phase with the reference signal phase.
10. The method of claim 8 , further comprising:
aligning the receive enable signal, the read data strobe signal, the write data strobe signal, and the center of the write data eye for each of a plurality of ranks in the memory.
11. The method of claim 8 , further comprising setting an alignment complete flag when all signal alignment operations are complete and no error flags are set in the alignment error register.