Method for changing ownership of a bus between master/slave devices
A system may comprise multiple master/slave devices coupled to a common bus, where one of the devices may operate as the current master device and the other devices may operate as current slave devices. Current slave devices may embed bus ownership request information within response packets transmitted in response to standard bus operations, such as reads and writes, issued by the current master device. When the current master device is idle, its bus interface may continually poll the current slave devices at regular intervals, according to a specified protocol, to ascertain whether any of them are requesting bus ownership. A response to a request for bus ownership received by the current master device may be configured according to desired system functionality. In one system, ownership may always be transferred to the requesting device. In other systems, the current master device may transmit a subsequent standard bus operation request packet, or a unique response packet, either comprising embedded information indicating whether ownership of the bus has been granted.
1. A method for changing ownership of a bus, the method comprising:
a first device of a plurality of devices having ownership of a serial bus and initiating a bus operation over the serial bus by transmitting a request data packet over the serial bus;
a second device of the plurality of devices receiving the request data packet over the serial bus, and recognizing the initiated bus operation on the serial bus in response to receiving the request data packet;
the second device transmitting a response data packet over the serial bus to the first device in response to said recognizing the initiated bus operation, wherein the response data packet comprises:
information specifically in response to the request data packet; and
request of ownership information indicating that the second device is requesting ownership of the serial bus;
the first device receiving the response data packet over the serial bus; and
the first device responding to the request of ownership information over the serial bus.
2. The method of claim 1 , further comprising a bus interface, coupled to the first device, issuing a request for ownership inquiry status.
3. The method of claim 2 , further comprising:
the second device receiving the request for ownership inquiry status; and
the second device transmitting an ownership request status response in response to said receiving the request for ownership inquiry status.
4. The method of claim 3 , wherein the ownership request status response comprises request of ownership information indicating that the second device is requesting ownership of the serial bus.
5. The method of claim 3 , wherein said issuing a request for interrupt status comprises transmitting a request packet, wherein the request packet comprises ownership inquiry data indicating that the request packet is the request for ownership inquiry status.
6. The method of claim 5 , wherein said transmitting the ownership request status response comprises transmitting an ownership request status packet, wherein the ownership request status packet comprises request of ownership information indicating that the second device is requesting ownership of the serial bus.
7. The method of claim 1 , wherein the request data packet is one of:
a read request packet; and
a write request packet.
8. The method of claim 1 , wherein said the first device responding to the request of ownership information comprises one or more of:
the first device relinquishing ownership of the serial bus to the second device;
the first device transmitting a request for an additional bus operation, wherein the request for the additional bus operation comprises response information corresponding to the request of ownership information; or
the first device transmitting a unique response indicating whether the second device's request of ownership of the serial bus is granted or denied.
9. A system comprising:
a bidirectional serial bus;
a first device configured to initiate bus operations over the bidirectional serial bus when having ownership of the bidirectional serial bus by sending out bus operation requests over the bidirectional serial bus; and
a second device configured to receive the bus operation requests over the bidirectional serial bus, and recognize the bus operations in response to receiving the bus operation requests over the bidirectional serial bus, wherein the second device is further configured to issue a respective bus operation response over the bidirectional serial bus for one or more of the bus operations recognized by the second device, wherein the second device is configured to include in one or more of the respective bus operation responses that the second device issues:
information specifically in response to the bus operation; and
ownership request information indicating that the second device is requesting ownership of the bidirectional serial bus.
10. The system of claim 9 further comprising a clock line coupled between the first device and the second device, wherein the first device is configured to generate a clock signal and to transmit the clock signal over the clock line.
11. The system of claim 9 , wherein the bidirectional serial bus is a single-wire bus.
12. The system of claim 9 , further comprising a bus interface coupled between the first device and the bidirectional serial bus, wherein the bus interface comprises a protocol configured to issue one or more ownership request inquiry commands to ascertain whether the second device is requesting ownership of the bidirectional serial bus.
13. The system of claim 12 , wherein the system is configured to programmatically specify a rate at which the one or more ownership request inquiry commands are issued when there is no activity on the bidirectional serial bus.
14. The system of claim 13 , wherein the rate at which the one or more ownership request inquiry commands are issued when there is no activity on the bidirectional serial bus comprises a slowest rate allowed by the system's request/grant response.
15. The system of claim 9 , wherein each of the bus operation requests comprises a request data packet, wherein each respective bus operation response issued by the second device comprises a response data packet, wherein the ownership request information is comprised in the response data packet when the respective bus operation response issued by the second device comprises ownership request information.
16. The system of claim 9 , wherein each of the bus operation requests comprises one of:
a read request; and
a write request.
17. A system comprising:
a bidirectional serial bus; and
a plurality of devices, each of the plurality of devices coupled to the bidirectional data bus, wherein each of the plurality of devices is:
configured to initiate bus operations over the bidirectional data bus when having ownership of the bidirectional data bus;
configured to recognize the bus operations on the bidirectional data bus;
configured to issue respective bus operation responses over the bidirectional data bus for the recognized bus operations;
configured to include in the respective bus operation responses:
information specifically in response to the bus operation; and
ownership request information indicating respective requests for ownership of the bidirectional data bus; and
configured to receive the respective bus operation responses over the bidirectional data bus.
18. The system of claim 17 , wherein each of the plurality of devices is configured to respond, when having ownership of the bidirectional serial bus, to the respective requests for ownership of the bidirectional serial bus.
19. The system of claim 18 , wherein in responding to any one of the respective requests for ownership of the bidirectional serial bus, each of the plurality of devices is configured to perform one or more of:
relinquish ownership of the bidirectional serial bus according to the ownership request information;
transmit a request for an additional bus operation, wherein the request for the additional bus operation comprises response information corresponding to the respective request for ownership of the bidirectional serial bus; and
transmit a unique response indicating whether the respective request for ownership of the bidirectional serial bus is granted or denied.
20. The system of claim 19 , further comprising a clock line coupled between each of the plurality of devices, wherein each of the plurality of devices is configured to generate a respective clock signal and transmit the respective clock signal over the clock line.
21. The system of claim 17 ;
wherein each of the plurality of devices comprises a respective one of a plurality of bus interfaces, each of the plurality of bus interfaces configured to operate according to a specified protocol;
wherein a device of the plurality of devices that is currently master of the bidirectional serial bus is designated as a master device;
wherein according to the specified protocol, the bus interface comprised in the master device is configured to issue one or more ownership request inquiry commands to ascertain whether any of the plurality of devices other than the master device are requesting ownership of the bidirectional serial bus.
22. The system of claim 21 , wherein the bus interface comprised in the master device is configured to issue the one or more ownership request inquiry commands when the master device is idle.
23. The system of claim 21 , wherein any of the plurality of devices that is not the master device is configured to receive the one or more ownership request inquiry commands.
24. The system of claim 23 , wherein any one of the plurality of devices that receives at least one of the one or more ownership request inquiry commands is configured to respond to the received at least one ownership request inquiry command.
25. The system of claim 24 , wherein in responding to the received at least one ownership request inquiry command, the any one of the plurality of devices is configured to transmit a bus ownership request to the master device.
26. The system of claim 25 , wherein the master device is configured to receive the bus ownership request, wherein in response to receiving the bus ownership request the master device is configured to perform one of:
relinquish ownership of the bidirectional serial bus according to the bus ownership request; or
retain ownership of the bidirectional serial bus.
27. The system of claim 26 , wherein the any one of the plurality of devices is configured to transmit the bus ownership request to the master device multiple times until the master device relinquishes ownership of the bidirectional serial bus.
28. The system of claim 25 , wherein the bus ownership request comprises a bus ownership request packet.
29. The system of claim 21 , wherein the one or more ownership request inquiry commands comprise ownership request inquiry packets.
30. The system of claim 17 , wherein the bus operation requests comprise one or more of:
read requests; and
write requests.
31. The system of claim 17 , wherein the bus operation requests comprise bus operation request packets.
32. The system of claim 17 , wherein the plurality of devices comprises master/slave devices.