Serial device daisy chaining method and apparatus

• US 20030074505A1
• Filed: 10/15/2001
• Published: 04/17/2003
• Est. Priority Date: 10/15/2001
• Status: Active Grant

• Current Assignee: Skyworks Solutions Incorporated
• Original Assignee: Christopher D. Eckhoff, David C. Andreas, Richard D. Loveman
• Inventors: Loveman, Richard D., Eckhoff, Christopher D., Andreas, David C.
• Granted Patent: US 6,928,501 B2
• Time in Patent Office: Days
• US Class Current: 710/110
• CPC Class Codes: G06F 13/4256 using a clocked protocol

Abstract

Methods and apparatus associated with a plurality of serial devices designed to communicate with a bus master in either a daisy chain or a normal configuration are provided. One method includes the step of serially providing a command sequence having a channel identifier to a given device of a plurality of daisy chained devices. The channel identifier is modified as it passes thru each daisy chained device. A specific device is identified or enabled when the channel identifier it receives matches a pre-determined value.

Claims

1. A method comprising the steps of:

a) serially providing a command sequence containing a first channel identifier to a first device of a plurality of daisy chained devices; and

b) modifying the first channel identifier to generate a second channel identifier for transmission to the next device in the daisy chain.

2. The method of claim 1 wherein the command sequence includes a command word, an address word, and at least one data word.

3. The method of claim 1 further comprising the step of:

c) executing a command of the command sequence on any device receiving the command, if that device has a received channel identifier matching a pre-determined value, wherein each of the plurality of devices uses the same pre-determined value for comparison.

4. The method of claim 3 wherein the pre-determined value is a selected member of the set {x0h, xFh}.

5. The method of claim 1 wherein step b) further comprises the step of incrementing the first channel identifier to form the second channel identifier.

6. The method of claim 1 wherein step b) further comprises the step of decrementing the first channel identifier to form the second channel identifier.

7. The method of claim 1 wherein the first channel identifier is provided in least significant bit order within the command sequence.

8. The method of claim 1 further comprising the step of:

c) executing a command of the command sequence received by each device on that device independently of its associated received channel identifier, if a broadcast option is selected.

9. A serial device apparatus comprising:

a serial input port for receiving a first command sequence having a first channel identifier and a remaining command sequence;

a daisy chain output port; and

command sequence processing logic for modifying the first channel identifier to form a second channel identifier, wherein the command processing logic provides the second channel identifier and the remaining command sequence to the daisy chain output port.

10. The apparatus of claim 9 wherein the first channel identifier is incremented to form the second channel identifier.

11. The apparatus of claim 9 wherein the first channel identifier is decremented to form the second channel identifier.

12. The apparatus of claim 9 wherein the first channel identifier is stored in least significant bit order within the command sequence.

13. The apparatus of claim 9 further comprising:

command execution logic for executing the command if the first channel identifier matches a pre-determined value.

14. The apparatus of claim 13 wherein the pre-determined value is a selected member of the set {x0h, xFh}.

15. An apparatus comprising:

a bus master providing an initial command sequence having an initial channel identifier;

a plurality of serial devices, each device comprising;

a serial input port for receiving a first command sequence having a first channel identifier and a remaining command sequence;

a daisy chain output port; and

command sequence processing logic for modifying the first channel identifier to form a second channel identifier, wherein the command processing logic provides the second channel identifier and the remaining command sequence to the daisy chain output port;

a bus coupling the serial devices in one of a normal configuration and a daisy chain configuration.

16. The apparatus of claim 15 wherein the bus master provides the initial command sequence with the channel identifier selected from the set of {x0h, xFh} when the devices are coupled in the normal configuration, wherein each of the plurality of devices receives the initial command sequence substantially simultaneously.

17. The apparatus of claim 15 wherein when coupled in daisy chain configuration, the bus master provides the initial command sequence to a first serial device of the plurality of devices, wherein each subsequent device receives a modified command sequence including the second channel identifier and the remaining command sequence provided by a preceding serial device, wherein the plurality of second channel identifiers is distinct.

18. The apparatus of claim 15 wherein each serial device further comprises command execution logic, wherein the command execution logic executes the command sequence received by that device if the associated channel identifier matches a pre-determined value shared by the plurality of serial devices.

19. The apparatus of claim 18 wherein the pre-determined value is a selected member of the set {x0h, xFh}.

20. The apparatus of claim 15 wherein the bus master provides the initial channel identifier in least significant bit order within the initial command sequence, wherein the initial command sequence is provided in most significant bit order.