Method and apparatus for providing an interface between a host device and a plurality of storage devices

Abstract

An emulation circuit configured to emulate each of a master mode and a slave mode to provide an interface between a host device and a plurality of storage devices. The emulation circuit includes a first bus and a second bus. The emulation circuit includes a plurality of bridge circuits each configured to communicate with the host device over the first bus, communicate with a respective storage device of a plurality of storage devices over the second bus, and receive a mode select signal configured to set the bridge circuit to one of a host mode and a device mode. The bridge circuit is further configured to, if the mode select signal sets the bridge circuit to the host mode, select, based on an emulation select signal, between the master mode and the slave mode.

Description

TECHNICAL FIELD

This invention relates to Serial Advanced Technology Attachment (SATA) input/output (I/O) assemblies.

BACKGROUND

The Parallel ATA (Advanced Technology Attachment) specification has defined the standard storage interface for PCs since the early 1980s. Parallel ATA provides low cost, broad operating system support, and steady evolution. Over time, parallel ATA has continuously evolved to support higher speed and performance. However, due to several reasons, including performance headroom, cabling issues, and voltage tolerance requirements, a new storage interface known as Serial ATA has recently been created.

Serial ATA may combine software transparency, low cost, scalability, and design flexibility to overcome the limitations of parallel ATA. Point-to-point data rates of 1.5 Gbps may be attainable with Serial ATA. Although SATA provides many benefits over PATA, there remains a large installed user-base of PATA compatible storage devices and computers. To continue to use the existing PATA compatible storage devices, bridge devices have been developed to interface PATA devices to SATA compatible computer systems.

FIG. 1 shows a conventional computer system 10 that communicates information via a SATA link 11. The computer system 10 includes a device bridge 12 to interface a PATA storage device 14 to a host controller 16 through a host bridge 18. The device bridge 12 and the host bridge 18 may each convert PATA formatted information to SATA formatted information and SATA formatted information to PATA formatted information. The device bridge 12 and the host bridge are generally not interchangeable due to differences in the header information that each of the bridges 12 and 18 generate when converting information between the SATA to PATA formats.

SUMMARY

In one aspect, an interface circuit for interfacing a Parallel ATA bus to a storage device. The interface circuit including a storage device controller in communication with the storage device to control a flow of information between the storage device and a Serial ATA bus. The Serial ATA bus to carry information having a Serial ATA format. A bridge circuit configured as a host bridge to interface between the Serial ATA bus and the Parallel ATA bus. The host bridge to convert Serial ATA information to Parallel ATA information and to convert Parallel ATA information to Serial ATA information.

The details of one or more embodiments of the invention are set forth in the accompa-nying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram of a conventional interface circuit.

FIG. 2 is a block diagram of an aspect of an interface circuit.

FIG. 3 is a block diagram of an emulation aspect of an interface circuit.

FIG. 4 is a block diagram of a hot plug aspect of an interface circuit.

Like reference symbols in the various drawings indicate like elements.

DESCRIPTION

FIG. 2 shows an aspect of an interface circuit 50 for controlling the communication of streams of information between a PATA compliant bus 54 and a SATA compliant bus 58. The interface circuit 50 may be implemented in any type of assembly such as on a single semiconductor die and as a multi-chip module. A Complementary Metal Oxide Semiconductor (CMOS) fabrication process is particularly suitable for fabricating the interface circuit 50, however any type of fabrication process may be used.

A hard disk controller 56 controls the flow of information between the SATA compliant bus 58 and a storage device 52. The storage device 52 may be any device for storing information such as a hard disk drive (HDD) and a CD-ROM. The hard disk controller 56 may be any type of controller that may interface to a SATA compliant bus. The SATA compliant bus 58 is suitable for carrying information that is formatted in accordance with the SATA standard.

A bridge circuit 60 is connected between the Serial ATA compliant bus 58 and the Parallel ATA compliant bus 54. The bridge circuit 60 may be selected to be in a host mode or a device mode in which the bridge circuit operates respectively as a host bridge or a device bridge. In this aspect, the bridge circuit 60 operates as a host bridge to enable the use of low-cost, widely available Parallel ATA connectivity while using a high-speed Serial ATA controller 56 to interface to the storage device 52. The bridge circuit 60 may receive Serial ATA commands communicated over the Serial ATA compliant bus 58. The bridge circuit 60 may decode the commands and convert them to Parallel ATA device commands. For responses from the Parallel ATA bus 54, the bridge circuit 60 may decipher, process, and convert the responses to Serial ATA protocol and communicate the responses over the Serial ATA compliant bus 58.

A mode select input 62 of the bridge circuit 60 may set the operating mode of the bridge circuit 60. Supported operating modes may include modes such as host mode and device mode. In host mode, the bridge circuit 60 operates as a host bridge. In device mode, the bridge circuit 60 operates as a device bridge. The mode select input 62 is preferably a single digital input and may advantageously be set at any time during the operation of the interface circuit 50. However, the mode select input 62 may also be implemented as one or more digital and analog inputs or be received via a Universal Asynchronous Receiver-Transmitter (UART).

FIG. 3 shows an aspect of an interface circuit 70 for controlling the communication of streams of information between a PATA compliant bus 72 and two or more SATA compliant buses 74. The interface circuit 70 advantageously supports emulation of master/slave mode for attached storage devices 76 such as hard disk drives (HDDs) and CD-ROMs. The storage devices 76 may be PATA compliant or SATA compliant devices. For storage devices that are PATA compliant, bridge circuits 78 configured for device mode may interface between the SATA compliant buses 74 and PATA compliant buses 80 that connect to the storage devices 76. The bridge circuits 78 may include a mode select function that is set to device mode, or may be a single-mode bridge device.

An emulation circuit 82 may include two or more bridge circuits 84 to emulate master/slave mode for the storage devices 76. Each of the bridge circuits 84 connects between the PATA compliant bus 72 and corresponding ones of the SATA compliant buses 74. Each of the bridge circuits 84 may include a mode select input and an emulation select input.

The mode select input may receive a mode signal to set the bridge circuit 84 to either a host mode or a device mode. In this aspect, the bridge circuit 84 is preferably set to the host mode. When in host mode, the emulation select input may receive an emulation signal to set the bridge circuit 84 to an emulation state such as master, slave, and master/slave. The bridge circuit 84 emulates a storage device as a function of the emulation state indicated by the emulation signal.

FIG. 4 shows an aspect of an interface circuit 100 for controlling the communication of streams of information that flow between PATA compliant buses 102a and 102b and a SATA compliant bus 104. The interface circuit 100 is particularly suitable for a hot plugging operation between a host 106 and a storage device 108. Bridge circuits 110 and 112 correspond to the host 106 and the storage device 108. Each of the bridge circuits 110 and 112 may include a mode input 114 and a hot plug enable input 116. The mode input 114 may receive a mode signal to set the operating mode of the corresponding bridge circuit to a host mode or a device mode. The bridge circuits 110 and 112 are preferably configured in host mode and device mode respectively to correspond to the host 106 and the storage device 108.

The hot plug enable input 116 may receive a hot plug signal to enable or disable a hot plug mode. The bridge circuits 110 and 112 may also receive one or more of the hot plug signal and the mode signal via a communication device such as a UART. During hot plug mode, the bridge circuits may monitor the SATA compliant bus 104 to determine whether the SATA compliant bus has been disconnected or connected. For example, the bridge circuits may sense activity on the SATA compliant bus 104 to determine whether a hot plugging operation such as connecting or disconnecting has occurred.

In response to detecting a disconnecting operation, a signal may be sent to the operating system associated with the host 106 indicating that the storage device 108 has been disconnected. The bridges 110 and 112 may then monitor the SATA compliant bus 104 for activity such as an out of band (00B) sequence. If activity is detected on the SATA compliant bus 104, the operating system may be notified and the bridges 110 and 112 may independently initiate operations to establish a communication link between the host 106 and the storage device 108 such as resetting the PHY associated with each bridge 110 and 112.

A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. For example, a UART may be included in a bridge circuit for communicating information. The UART may receive inputs such as mode select, master/slave emulation, and hot plug enable and communicate those inputs to other circuits in the bridge circuit. Accordingly, other embodiments are within the scope of the following claims.

Claims

1. An emulation circuit configured to emulate, at different times, each of a master mode and a slave mode to provide an interface between a host device and a plurality of storage devices, the emulation circuit comprising: a first bus configured to carry information that is formatted in accordance with a first standard;a second bus configured to carry information that is formatted in accordance with a second standard, wherein the second standard is different from the first standard; anda plurality of bridge circuits, each of the plurality of bridge circuits configured to communicate, over the first bus, the information that is formatted in accordance with the first standard to the host device,communicate, over the second bus, the information that is formatted in accordance with the second standard to a respective storage device of the plurality of storage devices,receive a mode select signal configured to set the bridge circuit to either a host mode or a device mode, wherein when in the host mode, the bridge circuit is configured to operate as a host with respect to the respective storage device of the plurality of storage devices, and wherein when in the device mode, the bridge circuit is configured to operate as a device with respect to the host device, andif the mode select signal sets the bridge circuit to the host mode, select, based on an emulation select signal that is independent of the mode select signal, between the master mode and the slave mode such that, while set to the host mode, the bridge circuit is further configurable between the master mode and the slave mode, wherein in the master mode, the bridge circuit is configured to emulate a storage device configured to operate in the master mode, andin the slave mode, the bridge circuit is configured to emulate a storage device configured to operate in the slave mode.

2. The emulation circuit of claim 1, wherein the bridge circuit is further configured to select a master/slave mode based on the emulation select signal, and wherein, in the master/slave mode, the bridge circuit is configured to emulate a storage device configured to operate in each of the master mode and the slave mode.

3. The emulation circuit of claim 1, wherein the first bus corresponds to a parallel advanced technology attachment bus and the second bus corresponds to a serial advanced technology attachment bus.

4. The emulation circuit of claim 1, wherein when in the host mode, the bridge circuit is configured to convert serial information received via the second bus to parallel information to be provided to the first bus, andwhen in the device mode, the bridge circuit is configured to convert parallel information received via the first bus to serial information to be provided to the second bus.

5. The emulation circuit of claim 1, wherein the bridge circuit includes a mode select pin configured to receive the mode select signal.

6. The emulation circuit of claim 1, wherein the mode select signal corresponds to a single digital input.

7. The emulation circuit of claim 1, wherein the bridge circuit is configured to selectively operate in a hot plug mode in response to a hot plug signal, andwhen the bridge circuit is operating in the hot plug mode, the bridge circuit is configured to determine whether the second bus has been connected to or disconnected from the bridge circuit.

8. A system comprising the emulation circuit of claim 1, and further comprising: a second bridge circuit, external to the emulation circuit, connected between one of the plurality of bridge circuits and one of the plurality of storage devices.

9. A method of operating an emulation circuit including a plurality of bridge circuits, the emulation circuit configured to emulate, at different times, each of a master mode and a slave mode to provide an interface between a host device and a plurality of storage devices, the method comprising: using each of the plurality of bridge circuits, communicating, over a first bus, information that is formatted in accordance with a first standard to the host device,communicating, over a second bus, information that is formatted in accordance with a second standard to a respective storage device of the plurality of storage devices, wherein the second standard is different from the first standard,receiving a mode select signal configured to set the bridge circuit to either a host mode or a device mode,when in the host mode, operating the bridge circuit as a host with respect to the respective storage device of the plurality of storage devices,when in the device mode, operating the bridge circuit as a device with respect to the host device,if the mode select signal sets the bridge circuit to the host mode, selecting, based on an emulation select signal that is independent of the mode select signal, between the master mode and the slave mode, such that, while set to the host mode, the bridge circuit is further configurable between the master mode and the slave mode,in the master mode, emulating a storage device configured to operate in the master mode, andin the slave mode, emulating a storage device configured to operate in the slave mode.

10. The method of claim 9, further comprising, using the bridge circuit: selecting a master/slave mode based on the emulation select signal; andin the master/slave mode, emulating a storage device configured to operate in each of the master mode and the slave mode.

11. The method of claim 9, wherein the first bus corresponds to a parallel advanced technology attachment bus and the second bus corresponds to a serial advanced technology attachment bus.

12. The method of claim 9, further comprising, using the bridge circuit: when in the host mode, converting serial information received via the second bus to parallel information to be provided to the first bus, andwhen in the device mode, converting parallel information received via the first bus to serial information to be provided to the second bus.

13. The method of claim 9, further comprising receiving the mode select signal at a mode select pin of the bridge circuit.

14. The method of claim 9, wherein the mode select signal corresponds to a single digital input.

15. The method of claim 9, further comprising, using the bridge circuit: selectively operating in a hot plug mode in response to a hot plug signal; andwhen in the hot plug mode, determining whether the second bus has been connected to or disconnected from the bridge circuit.

16. The method of claim 9, and further comprising: connecting a second bridge circuit, external to the emulation circuit, between one of the plurality of bridge circuits and one of the plurality of storage devices.