Systems and methods for maintaining synchronicity during signal transmission
Systems and methods are disclosed for facilitating synchronous communications over an asynchronous communications link. Specifically, embodiments of the claimed invention provide systems and methods for transmitting high-speed signals while maintaining lock-step determinism using remote clock phase adjustments. Embodiments of the claimed invention also provide systems and methods for maintaining determinism through the use of synchronized time slice counters within the various components.
1 . A synchronized communications system comprising:
a transmitter comprising a data clock;
a receiver; and
an asynchronous communications link connecting the transmitter and the receiver;
wherein the transmitter is configured to establish an appropriate offset for the data clock in order to counteract the effect of a transmission delay between the transmitter and the receiver.
2 . The system of claim 1 , further comprising a round trip timer configured to measure the round trip time required to send a signal to the receiver over a dedicated datapath within the communications link and to receive an acknowledgement back, the round trip time used to calculate the transmission delay.
3 . The system of claim 1 , wherein the transmitter and receiver are located within a fault tolerant computer system.
4 . The system of claim 2 , wherein the transmitter further comprises a transmitter clock.
5 . The system of claim 4 , wherein the round trip timer measures the round trip time relative to the transmitter clock.
6 . The system of claim 5 , wherein the signal comprises a data clock component and a data component, the data clock component based upon the data clock.
7 . The system of claim 6 , wherein the receiver is configured to use the data clock component to process the data component.
8 . The system of claim 7 , wherein after the offset has been established, the data clock is adjusted such that all future signals communicated between the transmitter and the receiver use the adjusted data clock.
9 . A method for synchronizing a transmitter and a receiver, the transmitter having a transmitter clock and a data clock, the method comprising:
adding an offset to the data clock such that the transmitter and receiver operate in synchrony.
10 . The method of claim 9 , further comprising the step of calculating a transmission delay between the transmitter and receiver, such that the offset added to the data clock compensates for the transmission delay.
11 . The method of claim 10 , further comprising the step of transmitting a data clock signal from the transmitter to the receiver over a dedicated datapath, such that the receiver operates in lockstep with the transmitter through the use of the data clock signal.
12 . The method of claim 11 , wherein the transmitter and receiver are located within a fault-tolerant system.
13 . A method for synchronizing a transmitter and a receiver through the use of a signal, the transmitter having a transmitter clock and a data clock, the receiver having a receiver clock, the method comprising:
(a) transmitting the signal from the transmitter to the receiver over a dedicated datapath;
(b) transmitting an acknowledgement from the receiver to the transmitter over the dedicated datapath;
(c) calculating and recording a round trip transit time defining the period between when the signal was sent by the transmitter and the acknowledgement was received by the transmitter;
(d) adding an offset to the data clock;
(e) repeating steps (a) through (d) until a stopping condition has been reached; and
(f) thereafter, selecting a preferred offset and adjusting the data clock accordingly.
14 . The method of claim 13 , wherein the signal is a data clock signal based upon the data clock.
15 . The method of claim 14 , further comprising:
(g) after the data clock has been adjusted, transmitting all subsequent data components with adjusted data clock components based upon the adjusted data clock.
16 . The method of claim 15 , further comprising:
(h) using the adjusted data clock in the receiver to process the data component.
17 . The method of claim 13 , wherein the preferred offset is based upon the median round trip transit time.
18 . The method of claim 13 , wherein the preferred offset is based upon the average round trip transit time.
19 . The method of claim 13 , wherein the stopping condition comprises repeating steps (a) through (d) a predetermined number of times.
20 . The method of claim 13 , wherein the stopping condition comprises repeating steps (a) through (d) until the data clock has been measured for each possible phase of the transmit clock.
21 . The method of claim 13 , wherein, the step of adjusting the transmitter clock further comprises adjusting the phase of the data clock forward or backward with respect to the transmitter clock.
22 . The system of claim 1 , wherein the data clock comprises a clock-forwarded clock.