State change in systems having devices coupled in a chained configuration
The present disclosure includes methods, devices, and systems for state change in systems having devices coupled in a chained configuration. A number of embodiments include a host and a number of devices coupled to the host in a chained configuration. The chained configuration includes at least one device that is not directly coupled to the host. The at least one device that is not directly coupled to the host is configured to change from a first communication state to a second communication state responsive to receipt of a command from the host.
1. A system, comprising:
a host; and
a number of devices coupled to the host in a chained configuration, wherein the chained configuration includes:
a first device coupled to the host via a first link;
a second device coupled to the first device via a second link; and
a third device coupled to the second device via a third link;
wherein the third link is configured to:
change from a first state, where the first state is a low speed standby state, to a second state, where the second state is a low speed communication state, responsive to a first command from the host; and
change from the second state to a third state, where the third state is a high speed communication state, responsive to a second command from the host; and
wherein the second link is configured to change from the second state to the third state responsive to the second command from the host.
2. The system of claim 1 , wherein:
the host includes a host output port;
the first device includes a first input port and a first output port;
the second device includes a second input port and a second output port;
the third device includes a third input port;
the first link includes the host output port and the first input port;
the second link includes the first output port and the second input port; and
the third link includes the second output port and the third input port.
3. The system of claim 1 , wherein:
the host includes a host input port;
the first device includes a first output port and a first input port;
the second device includes a second output port and a second input port;
the third device includes a third output port;
the first link includes the host input port and the first output port;
the second link includes the first input port and the second output port; and
the third link includes the second input port and the third output port.
4. The system of claim 1 , wherein:
the host includes a host input port and a host output port;
the first device includes a first input port, a first output port, a second input port, and a second output port;
the second device includes a third input port, a third output port, a fourth input port, and a fourth output port;
the third device includes a fifth input port and a fifth output port;
the first link includes the host input port, the host output port, the first input port, and the first output port;
the second link includes the second input port, the second output port, the third input port, and the third output port; and
the third link includes the fourth input port, the fourth output port, the fifth input port, and the fifth output port.
5. The system of claim 1 , wherein:
the third link is configured to change from the low speed standby state to the low speed communication state responsive to receipt of the first command; and
the third link and the second link are configured to change from the low speed communication state to the high speed communication state responsive to receipt of the second command.
6. The system of claim 1 , wherein:
the third device is configured to send an acknowledgement of the first command to the host responsive to the change of the third link from the first state to the second state; and
the host is configured to send the second command responsive to receipt of the acknowledgement.
7. The system of claim 1 , wherein:
an amount of time is associated with changing the third link from the first state to the second state; and
the host is configured to send the second command responsive to an expiration of the amount of time.
8. The system of claim 1 , wherein the host is configured to send the second command without receiving an acknowledgement of the first command.
9. The system of claim 1 , wherein:
the first link is configured to communicate information at a rate in a first state that is as fast as or faster than an information communication rate of the second link in a second state and the third link in a third state; and
the second link is configured to communicate information at a rate in the second state that is as fast as or faster than the information communication rate of the third link in the third state.
10. The system of claim 1 , wherein the third link is configured to change from the low speed communication state to the high speed communication state responsive to receipt of the first command or the second command from the host.
11. The system of claim 1 , wherein the second link is configured to change from the low speed communication state to the high speed communication state responsive to receipt of the second command from the host.
12. A system, comprising:
a host;
a first device directly coupled to the host via a first link;
a second device directly coupled to the first device via a second link; and
a third device directly coupled to the second device via a third link, wherein the third link is configured to:
change from a first state to a second state responsive to receipt of a first command from the host, wherein the first state is a lower speed state than the second state; and
change from the second state to a third state responsive to receipt of a second command from the host, wherein the second state is a lower speed state than the third state.
13. The system of claim 12 , wherein
the second link is configured to change from the second state to the third state responsive to receipt of the second command from the host.
14. A method of operating a system, comprising:
directly coupling a first device to a host;
directly coupling a second device to the first device;
directly coupling a third device to the second device via a link; and
changing the link from a first state to a second state responsive to a command from the host, wherein the first state is a low speed communication state, and the second state is a high speed communication state.
15. The method of claim 14 , wherein the method includes changing the link from the second state to the third state responsive to an additional command from the host.