Controlling passthrough of communications between multiple buses

• US 20090292843A1
• Filed: 05/21/2008
• Published: 11/26/2009
• Est. Priority Date: 05/21/2008
• Status: Active Grant

• Current Assignee: Silicon Laboratories Incorporated
• Original Assignee: Silicon Laboratories Incorporated
• Inventors: Sun, Ruifeng, Hester, Dylan, Haban, Scott
• Granted Patent: US 7,882,282 B2
• Time in Patent Office: Days
• US Class Current: 710/110
• CPC Class Codes: G06F 13/4282 on a serial bus, e.g. I2C bus, SPI bus on daisy chain buses G06F13/4247

Abstract

A demodulator can include first data and clock pads to couple the demodulator to a host device via a first bus, and second data and clock pads to couple the demodulator to a radio frequency (RF) tuner via a second bus. The device may further include passthrough logic to couple host data and a host clock from the first bus to the second bus and to couple tuner data from the second bus to the first bus during a passthrough mode. During this mode, however, the two buses may remain electrically decoupled. When the passthrough mode is disabled, the RF tuner is thus shielded from noise present on the first bus.

Claims

1. A demodulator comprising:

a first data pad and a first clock pad to couple the demodulator to a host device via a first bus;

a second data pad and a second clock pad to couple the demodulator to a radio frequency (RF) tuner via a second bus; and

passthrough logic to couple host data and a host clock from the first bus to the second bus and to couple tuner data from the second bus to the first bus during a passthrough mode, wherein the first and second buses are electrically decoupled during the passthrough mode.

2. The demodulator of claim 1, further comprising a first input path from the first data pad to a slave controller of the demodulator and a second input path from the first data pad to the second data pad, wherein the first input path comprises a filtered path and the second input path comprises an unfiltered path.

3. The demodulator of claim 1, wherein the passthrough mode between the host device and the RF tuner is controlled by the host device.

4. The demodulator of claim 3, wherein the host device is to write a passthrough enable indicator to the demodulator to enable the passthrough mode, the passthrough mode to begin at an end of a data transaction from the host device including the passthrough enable indicator.

5. The demodulator of claim 3, wherein the host device is to enable the passthrough mode to provide information to the RF tuner and to disable the passthrough mode when the host device is to provide information the demodulator.

6. The demodulator of claim 3, further comprising a slave controller of the demodulator to snoop passthrough communications during the passthrough mode and to control a direction of the passthrough communications through the first data pad and the second data pad.

7. A system comprising:

a host device coupled to a first bus, the first bus coupled to a plurality of slave devices;

a first slave device coupled to the host device via the first bus and including a slave state machine to handle receipt and transmission of information on the first bus; and

a second slave device coupled to the first slave device via a second bus, wherein the slave state machine of the first slave device is to enable mirrored communication along the first bus to the second slave device via the second bus under control of the host device, the mirrored communication to begin at an end of a transaction from the host device to the first slave device including a mirrored communication command.

8. The system of claim 7, wherein the first slave device further comprises passthrough logic to buffer the communication along the first bus to the second bus without a direct electrical connection between the first and second buses.

9. The system of claim 7, wherein the first slave device includes:

a first data pad coupled to the first bus;

a second data pad coupled to the second bus;

a first input path from the first data pad to a slave controller of the first slave device; and

a second input path from the first data pad to the second data pad, wherein the first input path comprises a filtered path and the second input path comprises an unfiltered path.

10. The system of claim 9, wherein the first slave device includes:

a first output path from the slave controller of the first slave device to the first data pad; and

a second output path from the second data pad to the first data pad, wherein the first output path comprises a delayed path and the second output path comprises an undelayed path.

11. The system of claim 7, wherein the first slave device further comprises a first delay element clocked by a data signal of the first bus and to change state only when a clock signal of the first bus is in a high state.

12. The system of claim 11, wherein the mirrored communication is to begin when the first delay element changes state to an enable mode for the mirrored communication.

13. The system of claim 12, wherein the enable mode is to begin when a stop signal for the transaction is received from the host device coincident when the clock signal is in the high state.

14. A method comprising:

determining whether a passthrough command has been received within a transaction from a host to a first slave device on a first bus;

setting a passthrough mode indicator in a control register of the first slave device when the passthrough command has been received;

providing a passthough enable signal at an end of the transaction from a state machine of the first slave device to a passthrough circuit of the first slave device to enable a passthrough mode; and

buffering communications between the first bus and a second bus coupled between the first slave device and a second slave device in the passthrough mode.

15. The method of claim 14, further comprising snooping data and control information communicated on the first and second buses in the state machine of the first slave device and analyzing the data and control information to determine a direction of communication flow between the host and the second slave device.

16. The method of claim 15, further comprising controlling the direction of communication flow via transmission of a direction signal from the state machine of the first slave device to the passthrough circuit based on the snooping.

17. The method of claim 14, further comprising providing the communications from an input pad of the first slave device to the state machine of the first slave device on a first parallel path, and providing the communications from the input pad to an output pad of the first slave device coupled to the second bus on a second parallel path.

18. The method of claim 17, further providing the communications on the first parallel path corresponding to a filtered path, and providing the communications on the second parallel path corresponding to an unfiltered path.

19. The method of claim 14, further comprising buffering the communications without electrically coupling the first and second buses.

20. An integrated circuit comprising:

an analog front end to receive incoming modulated tuner signals via a first link with a tuner and to convert the incoming modulated tuner signals to a digital bitstream;

a demodulator coupled to the analog front end to receive the digital bitstream and to demodulate the digital bitstream into a demodulated bitstream to be provided to a host processor;

a first bus interface coupled to a first bus coupled between the integrated circuit and the host processor, the first bus interface including a first data pad coupled to the first bus, a first input path from the first data pad to a slave controller of the demodulator, a second input path from the first data pad to a second data pad of a second bus interface, wherein the first input path comprises a filtered path and the second input path comprises an unfiltered path, a first output path from the slave controller to the first data pad, and a second output path from the second data pad to the first data pad, wherein the first output path comprises a delayed path and the second output path comprises an undelayed path;

the second bus interface coupled to a second bus coupled between the integrated circuit and the tuner, the second bus interface including the second data pad coupled to the second bus, a third input path from the second data pad to the slave controller, a fourth input path from the second data pad to the first data pad, wherein the third input path comprises a filtered path and the fourth input path comprises an unfiltered path, a third output path from the slave controller to the second data pad, and a fourth output path from the first data pad to the second data pad, wherein the third output path comprises a delayed path and the fourth output path comprises an undelayed path; and

a passthrough circuit coupled to the first and second bus interfaces to buffer data between the first bus to the second bus along the second and fourth input paths and the second and fourth output paths.

21. The integrated circuit of claim 20, wherein the passthrough circuit is to buffer the data without electrically coupling the first and second buses.

22. The integrated circuit of claim 20, wherein the slave controller of the demodulator is to snoop the data buffered through the passthrough circuit and to control a direction of the data through the first data pad and the second data pad.

23. The integrated circuit of claim 22, wherein the slave controller is to control the direction of the data via transmission of a direction signal from a state machine of the slave controller to the passthrough circuit based on the snooping.

24. The integrated circuit of claim 20, wherein the demodulator is to receive a passthrough enable indicator from the host processor to enable the buffered data and to begin passthrough of the buffered data at an end of a transaction from the host processor including the passthrough enable indicator.