Devices and methods for transmission of events with a uniform latency on serial communication links
The present disclosure relates generally to serial communication links and, more specifically, to events communicated on serial communication links and the timing of those events, for example, to achieve uniform delay among multiple event transmissions.
1. A serial communication link transmitter, comprising:
delay circuitry configured to determine an event delay between a predefined bit position of an ongoing frame being transmitted and an event; and
transmission circuitry configured to send an event frame after the ongoing frame, wherein the transmission circuitry is configured to include in the event frame, delay bits indicative of the event delay and event identifier bits indicative of the event to which the event frame corresponds.
2. The serial communication link transmitter of claim 1 , wherein the delay circuitry comprises a delay counter configured to determine the event delay by counting a number of clocks from the event to the predefined bit position of the ongoing frame.
3. The serial communication link transmitter of claim 1 , further comprising:
two or more event sub-modules, wherein a first of the two or more event sub-modules corresponds to a first event type and a second of the two or more event sub-modules corresponds to a second event type, and
priority logic configured to associate a different priority with each of the first event type and the second event type.
4. The serial communication link transmitter of claim 1 , further comprising priority logic, and wherein responsive to an occurrence of a first event corresponding to a first event type and a second event corresponding to a second event type the priority logic is configured to:
transmit one of the first event and the second event with a higher priority; and
discard one of the first event and the second event with a lower priority.
5. The serial communication link transmitter of claim 1 , further comprising priority logic, and wherein responsive to an occurrence of a first event corresponding to a first event type and a second event corresponding to a second event type the priority logic is configured to:
transmit a higher priority event frame corresponding to one of the first event and the second event with a higher priority;
hold one of the first event and the second event with a lower priority while the higher priority event frame is transmitted; and
transmit a lower priority event frame corresponding to one of the first event and the second event with the lower priority after the higher priority event frame is transmitted, the lower priority event frame including an error bit.
6. The serial communication link transmitter of claim 1 , wherein the transmission circuitry is configured to send the event frame back-to-back with the ongoing frame.
7. The serial communication link transmitter of claim 1 , wherein the transmission circuitry is configured to encode frames based on a protocol selected from a group consisting of a Universal Asynchronous Receiver/Transmitter, a Universal Synchronous Receiver/Transmitter, or a Universal Synchronous/Asynchronous Receiver/Transmitter.
8. The serial communication link transmitter of claim 1 , wherein the transmission circuitry is further configured to include event identifier bits in the event frame, wherein the event identifier bits indicate which event of a set of events the event frame corresponds to.
9. The serial communication link transmitter of claim 1 , wherein the transmission circuitry is configured to include in the event frame one or more error bits indicative of whether the event frame was delayed for a period longer than a frame time.
10. The serial communication link transmitter of claim 1 , wherein the transmission circuitry is configured to, responsive to the event frame being delayed for a period longer than a frame time, encode an error signature in the delay bits, the error signature indicative of a delay time longer than a frame time.
11. The serial communication link transmitter of claim 1 , wherein the predefined bit position of an ongoing frame is a start of the ongoing frame.
12. A method of transmitting events over a serial communication link, comprising:
determining an event delay between a predefined bit position of an ongoing frame being transmitted and an event;
encoding an event frame indicative of the event, wherein the event frame includes:
delay bits indicative of the event delay; and
event identifier bits that indicate the event frame corresponds to the event, and transmitting the event frame after the ongoing frame.
13. The method of claim 12 , further comprising sending the event frame back-to-back with the ongoing frame.
14. The method of claim 12 , further comprising determining the event delay by counting a number of clocks from the event to the predefined bit position of the ongoing frame.
15. The method of claim 12 , further comprising:
responsive to an occurrence of a first event corresponding to a first event type and a second event corresponding to a second event type:
transmitting one of the first event and the second event with a higher priority; and
discarding of the first event and the second event with a lower priority.
16. The method of claim 12 , further comprising:
responsive to an occurrence of a first event corresponding to a first event type and a second event corresponding to a second event type:
transmitting a higher priority event frame corresponding to one of the first event and the second event with a higher priority;
holding one of the first event and the second event with a lower priority while the higher priority event frame is transmitted; and
transmitting a lower priority event frame corresponding to one of the first event and the second event with the lower priority after the higher priority event frame is transmitted, the lower priority event frame including an error bit.
17. The method of claim 12 , further comprising including in the event frame one or more error bits indicative of whether the event frame was delayed for a period longer than a frame time.
18. The method of claim 12 , further comprising, responsive to the event frame being delayed for a period longer than a frame time, encoding an error signature in the delay bits, the error signature indicative of a delay time longer than a frame time.
19. The method of claim 12 , wherein the predefined bit position of an ongoing frame is a start of the ongoing frame.