Latency adjustment between integrated circuit chips
View Patent ↗In emulation systems having a plurality of chips, data communicated between the chips needs to be synchronized. A receiver chip may push or pull on incoming data from an emitter chip in order to synchronize it with a receiver clock. Unexpected latency on the link between the emitter and receiver chips may also be adjusted for.
1. A method for adjusting for latency in a chip-to-chip link, comprising:
defining an expected latency associated with the link;
receiving a starter signal at a first chip and a second chip;
responsive to the first chip receiving the starter signal, the first chip sending a latency adjustment signal to the second chip over the link;
the second chip measuring a latency between the second chip receiving the starter signal and the second chip receiving the latency adjustment signal;
the second chip comparing the measured latency with the expected latency; and
the second chip adding a delay to the link based on the comparison of the measured latency with the expected latency.
2. The method, of claim 1 , wherein the step of receiving includes receiving the starter signal simultaneously to the first and the second chips.
3. The method of claim 1 , wherein the latency adjustment signal includes a predetermined serial pattern of bits including at least a zero bit and a one bit.
4. The method of claim 1 , wherein the latency adjustment signal includes a predetermined serial pattern of three bits.
5. The method of claim 1 , wherein the first and the second chips operate in response to a clock signal having a regular period, and wherein the delay is a whole number of one or more of the periods.
6. The method of claim 1 , wherein the delay is equal to a difference between the measured and the expected latency.
7. The method of claim 1 , wherein sending the latency adjustment signal includes sending a predetermined serial pattern of bits followed by a continuous pattern of alternating zero and one bits over the link.
8. A system for adjusting for latency in a chip-to-chip link, comprising:
a first chip coupled to a link, the first chip configured to receive a starter signal and to send a latency adjustment signal over the link in response to receiving the starter signal; and
a second chip coupled to the link and configured to receive the starter signal, the second chip further configured to measure a latency between the second chip receiving the starter signal and the second chip receiving the latency adjustment signal over the link, the second chip further configured to compare the measured latency with a predetermined expected latency, the second chip further configured to add a delay to the link based on the comparison of the measured latency with the expected latency.
9. The system of claim 8 , wherein the system is configured such that the starter signal is received simultaneously by the first and the second chips.
10. The system of claim 8 , wherein the latency adjustment signal includes a predetermined serial pattern of bits including at least a zero bit and a one bit.
11. The system of claim 8 , wherein the latency adjustment signal includes a predetermined serial pattern of three bits.
12. The system of claim 8 , wherein the first and second chips are configured to operate in response to a clock signal having a regular period, and wherein the second chip is configured to add the delay as a whole number of one or more of the periods.
13. The system of claim 8 , wherein the second chip is configured to add the delay by an amount equal to a difference between the measured latency and the expected latency.
14. The system of claim 8 , wherein the second chip includes a plurality of delay units coupled in series, the second chip configured to select one or more of the delay units to cause the delay to be added.
15. The system of claim 8 , wherein sending the latency adjustment signal over the link includes sending a predetermined serial pattern of bits followed by a continuous pattern of alternating zero and one bits over the link.