I3C single data rate write flow control
Systems, methods, and apparatus for communication over a serial bus in accordance with an I3C protocol are described that enable a slave device to request that a bus master device terminate a write transaction with the slave device. The serial bus may be operated according to an I3C single data rate protocol. In various aspects of the disclosure, a method performed at a master device coupled to a serial bus includes initiating a write transaction between the master device and a slave device, where the write transaction includes a plurality of data frames, and at least one data frame is configured with a transition bit in place of a parity bit. The method may include terminating the write transaction when the slave device drives a data line of the serial bus while receiving the transition bit.
1. A method performed at a master device coupled to a serial bus, comprising:
initiating a write transaction between the master device and a slave device, wherein the write transaction includes a plurality of data frames to be transmitted over a data line of the serial bus;
transmitting a transition bit from the master device in place of a parity bit of a first data frame while transmitting the first data frame to the slave device; and
terminating the write transaction when the slave device is determined to be driving the data line of the serial bus while the transition bit is being transmitted from the master device over the data line of the serial bus.
2. The method of claim 1 , wherein terminating the write transaction comprises:
transmitting signaling corresponding to a repeated START condition defined by a protocol used to control communications over the serial bus.
3. The method of claim 2 , wherein terminating the write transaction further comprises:
transmitting signaling corresponding to a STOP condition defined by the protocol used to control communications over the serial bus after transmitting the repeated START condition.
4. The method of claim 1 , wherein terminating the write transaction comprises:
transmitting signaling corresponding to a STOP condition defined by a protocol used to control communications over the serial bus.
5. The method of claim 1 , further comprising:
providing the transition bit in the first data frame by driving the data line of the serial bus to a high state after data bits of the first data frame have been transmitted; and
causing a line driver coupled to the data line to enter a high impedance mode after driving the data line of the serial bus to the high state.
6. The method of claim 5 , wherein the data line is maintained at the high state by a pull-up structure.
7. The method of claim 5 , wherein the high impedance mode comprises an open-drain mode.
8. The method of claim 5 , further comprising:
detecting a low state on the data line in a bit interval reserved for the transition bit; and
terminating the write transaction after detecting the low state on the data line.
9. The method of claim 1 , wherein the serial bus is operated in accordance with an I3C single data rate protocol.
10. An apparatus adapted to operate as a master device when coupled to a serial bus, the apparatus comprising:
a bus interface circuit configured to couple the apparatus to the serial bus; and
a processing device configured to:
initiate a write transaction between the apparatus and a slave device, wherein the write transaction includes a plurality of data frames to be transmitted over a data line of the serial bus;
transmit a transition bit from the apparatus in place of a parity bit of a first data frame while transmitting the first data frame to the slave device; and
terminate the write transaction when the slave device is determined to be driving the data line of the serial bus while the transition bit is being transmitted from the apparatus over the data line of the serial bus.
11. The apparatus of claim 10 , wherein the processing device is further configured to:
transmit signaling corresponding to a repeated START condition defined by a protocol used to control communications over the serial bus.
12. The apparatus of claim 11 , wherein the processing device is further configured to:
transmit signaling corresponding to a STOP condition defined by the protocol used to control communications over the serial bus after transmitting the repeated START condition.
13. The apparatus of claim 10 , wherein the processing device is further configured to:
transmit signaling corresponding to a STOP condition defined by a protocol used to control communications over the serial bus.
14. The apparatus of claim 10 , wherein the processing device is further configured to:
provide the transition bit in the first data frame by driving the data line of the serial bus to a high state after data bits of the first data frame have been transmitted; and
cause a line driver coupled to the data line to enter a high impedance mode after driving the data line of the serial bus to the high state.
15. The apparatus of claim 14 , wherein the processing device is further configured to:
detect a low state on the data line in a bit interval reserved for the transition bit; and
terminate the write transaction after detecting the low state on the data line.
16. A method performed at a slave device coupled to a serial bus, comprising:
receiving a configuration command from a master device indicating that data frames transmitted during a write transaction include transition bits in place of parity bits;
receiving a first data frame from a data line of the serial bus during the write transaction; and
driving the data line to assert a flow control request while receiving a first transition bit of the first data frame from the data line.
17. The method of claim 16 , further comprising:
receiving signaling corresponding to a repeated START condition after asserting the flow control request, the repeated START condition being defined by a protocol used to control communications over the serial bus.
18. The method of claim 17 , further comprising:
receiving signaling corresponding to a STOP condition after receiving the repeated START condition.
19. The method of claim 16 , further comprising:
receiving signaling corresponding to a STOP condition defined by a protocol used to control communications over the serial bus after asserting the flow control request.
20. The method of claim 16 , wherein the first transition bit of the first data frame is provided on the data line after eight data bits of the first data frame have been received.
21. The method of claim 16 , wherein the data line is maintained in a high state by a pull-up structure prior to assertion of the flow control request, further comprising:
driving the data line to a low state to assert the flow control request.
22. The method of claim 16 , wherein the serial bus is operated in accordance with an I3C single data rate protocol.
23. An apparatus adapted to operate as a slave device when coupled to a serial bus, the apparatus comprising:
a bus interface circuit configured to couple the apparatus to the serial bus; and
a processing device configured to:
receive a configuration command from a master device indicating that data frames transmitted during a write transaction include transition bits in place of parity bits;
receive a first data frame from a data line of the serial bus during the write transaction; and
cause the bus interface circuit to assert a flow control request by driving the data line while a first transition bit of the first data frame is being received from the data line.
24. The apparatus of claim 23 , wherein the processing device is further configured to:
receive signaling corresponding to a repeated START condition after asserting the flow control request, the repeated START condition being defined by a protocol used to control communications over the serial bus.
25. The apparatus of claim 24 , wherein the processing device is further configured to:
receive signaling corresponding to a STOP condition after receiving the repeated START condition.
26. The apparatus of claim 23 , wherein the processing device is further configured to:
receive signaling corresponding to a STOP condition defined by a protocol used to control communications over the serial bus after asserting the flow control request.
27. The apparatus of claim 23 , wherein the first transition bit of the first data frame is provided on the data line after eight data bits of the first data frame have been received.
28. The apparatus of claim 23 , wherein the data line is maintained in a high state by a pull-up structure prior to assertion of the flow control request, wherein the processing device is further configured to:
cause the bus interface circuit to drive the data line to a low state to assert the flow control request.
29. The apparatus of claim 23 , wherein the serial bus is operated in accordance with an I3C single data rate protocol.