Flow control mechanisms on synchronous serial TDMA bus
A method of transmitting data allows flow control information to be transmitted with the user data over a synchronous bus. A channel is defined, identifying the source and at least one sink, and this includes the definition of a transport profile, indicating a flow control requirement for the data. Data is then transmitted from the source over the bus in at least one data time slot ( 30 ) and, if indicated by the transport profile, flow control information is also transmitted from the source over the bus in at least one flow control time slot ( 20 ) associated with the data time slot.
1. A method of transmitting data from a source to at least one sink over a synchronous TDMA wired bus, the method comprising:
defining a channel, by identifying the source and the at least one sink;
selecting a transport profile from a plurality of predefined transport profiles, wherein the selected transport profile indicates a flow control requirement for the data;
transmitting, from the source, to the at least one sink, a datum over the synchronous TDMA wired bus in a subframe consisting of a single data payload consisting of one or more data time slots, and a tag field consisting of one or more flow control time slots; and
when indicated by the selected transport profile, transmitting, from the source, to the at least one sink, flow control information over the synchronous TDMA wired bus in at least one flow control time slot in the tag field of the subframe, the flow control information being uniquely associated with only the datum transmitted during the same subframe.
2. The method of claim 1 , wherein one of the predefined transport profiles is a first profile that applies when the source is to push data to the at least one sink and the desired data rate is substantially equal to the channel rate.
3. The method of claim 2 , wherein the first profile indicates no flow control requirement, and hence no flow control information is transmitted from the source.
4. The method of claim 1 , wherein one of the predefined transport profiles is a second profile that applies when the source is to push the data to the at least one sink and a desired data rate is less than a channel rate.
5. The method of claim 4 , wherein, when the second profile is identified, the source sets a first flag during each flow control time slot in the tag field of the subframe, the first flag being associated with only the datum transmitted in the single data payload of the subframe.
6. The method of claim 5 , wherein each sink, on receipt of the first flag during the at least one flow control time slot in the tag field of the subframe, reads the datum transmitted in the single data payload of the subframe.
7. The method of claim 5 , wherein the at least one sink, on receipt of the first flag during the at least one flow control time slot in the tag field of the subframe, sets a second flag during the at least one flow control time slot in the tag field of the subframe.
8. The method of claim 7 , wherein the source applies the logical second flag set by the at least one sink to obtain a combined synchronization signal.
9. The method of claim 1 , wherein one of the predefined transport profiles is a third profile that applies when the at least one sink is to pull the data from the source.
10. The method of claim 9 , wherein, when the third profile is defined, the at least one sink sets a third flag during each flow control time slot in the tag field of the subframe, the third flag being associated with the datum transmitted in the single data payload of the subframe.
11. The method of claim 1 , wherein one of the predefined transport profiles is a fourth profile that applies when the datum is transferred from a first device initially identified as the source to a second device initially identified as the at least one sink, and when the datum is transferred from the second device initially identified as the at least one sink to the first device initially identified as the source.
12. The method of claim 11 , wherein each of the second device initially identified as the sink and the first device initially identified as the source sets a fourth flag during the at least one flow control time slot in order to indicate that the first device has the data for transmission.
13. The method of claim 12 , wherein, during the at least one flow control time slot in the tag field of the subframe in which the first device initially identified as the source sets the fourth flag, the first device initially identified as the source also sets a fifth flag.
14. The method of claim 13 , wherein, when the first device initially identified as the source has set the fourth flag, the first device initially identified as the source sets a sixth flag when the first device initially identified as the source is ready to send the datum.
15. The method of claim 14 ,
wherein, during the at least one flow control time slot in which the first device initially identified as the source sets the fourth flag, the second device initially identified as the at least one sink also reads the fifth flag, in order to determine whether the fifth flag has been set by the first device initially identified as the source;
wherein, when the fifth flag has been set by the first device initially identified as the source, the second device initially identified as the at least one sink does not attempt to transmit the datum; and
wherein, when the fifth flag has not been set by the first device initially identified as the source, the second device initially identified as the sink sets a sixth flag when the second device initially identified as the sink is ready to send the datum.
16. The method of claim 13 , wherein, when one of the first device and the second device has set the sixth flag, the other of the first device and the second device sets a seventh flag when the other of the first device and the second device is ready to receive the datum.
17. The method of claim 16 , wherein, when the other of the first device and the second device has set the seventh flag, the one of the first device and the second device begins transmitting the datum.
18. The method of claim 17 , wherein, when the one of the first device and the second device no longer has the datum for transmission, the one of the first device and the second device resets the fourth flag.
19. The method of claim 11 , wherein one of the predefined transport profiles is a fifth profile that applies when the datum is transferred from the first device initially identified as the source to the second device initially identified as the sink, or from the second device initially identified as the sink to the first device initially identified as the source, and corresponds to the fourth profile, and
wherein, when the fifth profile is defined, one of the first device and the second device transmitting the datum indicates during at least one auxiliary time slot in an auxiliary field of the subframe an amount of data to be transmitted in the single data payload of the subframe, wherein the single data payload includes the auxiliary field having the at least one auxiliary time slot.
20. The method of claim 11 , wherein the fourth profile is configured to emulate a universal asynchronous receive and transmit (UART) link.
21. The method of claim 1 , wherein the single data payload includes an auxiliary field having one or more auxiliary time slots.
22. A method of transmitting data from a source to at least one sink over a synchronous TDMA bus, the method comprising:
defining a channel, by identifying the source and the at least one sink;
selecting a transport profile from a plurality of predefined transport profiles, wherein the selected transport profile indicates a flow control requirement for the data;
transmitting a datum from the source over the synchronous TDMA bus in a subframe consisting of a single data payload consisting of one or more data time slots, and a tag field consisting of one or more flow control time slots; and
if indicated by the selected transport profile, transmitting flow control information from the source over the synchronous TDMA bus in at least one flow control time slot in the tag field of the subframe, the flow control information being uniquely associated with only the datum transmitted during the same subframe;
wherein one of the predefined transport profiles is a fourth profile that applies when the data may be transferred from a first device initially identified as the source to a second device initially identified as the sink, or from the second device initially identified as the sink to the first device initially identified as the source,
wherein the first device initially identified as the sink and the second device initially identified as the source each sets a fourth flag during the at least one flow control time slot in the tag field of the subframe in order to indicate that each has a datum for transmission, and
wherein, during the flow control time slot in which the first device initially identified as the source sets the fourth flag, the first device initially identified as the source also sets a fifth flag.
23. The method of claim 22 , wherein, when the first device initially identified as the source has set the fourth flag, the first device initially identified as the source sets a sixth flag when the first device initially identified as the source is ready to send the datum.
24. The method of claim 22 , wherein the single data payload includes an auxiliary field having one or more auxiliary time slots.