Method and Apparatus for Attaching Multiple Slave Devices to a Single Bus Controller Interface While Supporting Command Pipelining

• US 20090113097A1
• Filed: 10/30/2007
• Published: 04/30/2009
• Est. Priority Date: 10/30/2007
• Status: Active Grant

• Current Assignee: LinkedIn Corporation (Microsoft Corporation)
• Original Assignee: International Business Machines Corporation
• Inventors: Srinivasan, Prasanna, Drerup, Bernard Charles, Nicholas, Richard
• Granted Patent: US 7,865,644 B2
• Time in Patent Office: Days
• US Class Current: 710/110
• CPC Class Codes: G06F 13/385 for adaptation of a particular data processing system to different peripheral devices

Abstract

In a method and apparatus associated with a bus controller, a set of mechanisms are selectively added to the bus controller, as well as to slave devices connected to the bus controller. A mechanism is also added to one or more master devices connected to the bus controller, in order to provide the master devices with a transaction ordering capability. The added mechanisms collectively achieve the objective of supporting connection of multiple slave devices to a common controller interface, and at the same time allowing pipelined operation of the slave devices. One embodiment of the invention is directed to a method for use with a bus and an associated bus controller, wherein the bus controller has respective master and slave interfaces for use in selectively interconnecting master devices and slave devices. The method comprises the steps of connecting one or more of the master devices to one of the master interfaces, and connecting each of a plurality of slave devices to the same one of the slave interfaces. The method further comprises operating a connected master device to send multiple commands to a selected one of the connected slave devices in accordance with a command pipelining procedure.

Claims

1. A method for use with a bus and associated bus controller, wherein the bus controller has respective master and slave interfaces for use in selectively interconnecting master devices and slave devices, said method comprising the steps of:

connecting one or more of said master devices to one of said master interfaces of said bus controller;

connecting each of a plurality of slave devices to the same particular one of said slave interfaces of said bus controller; and

operating a selected master device to send multiple commands to selected connected slave devices in accordance with a command pipelining procedure.

2. The method of claim 1, wherein:

said command pipelining procedure includes sending a first command to a slave device, and then sending a second command to a slave device before an acknowledgement for said first command has been received back by said selected master device, from the slave device to which the first command was sent.

3. The method of claim 1, wherein:

signals from said particular slave interface are multi-dropped to each of said plurality of slave devices, and signals from respective slave devices of said plurality of slave devices are collectively transmitted in accordance with a logic OR procedure.

4. The method of claim 1, wherein:

each connected slave device, after receiving a command at a given time, responds to the received command a pre-specified number of clock periods after said given time.

5. The method of claim 1, wherein:

each one of said connected slave devices, in sending a response to one of said commands, includes a decode signal in the response that is unique to the sending slave device.

6. The method of claim 5, wherein:

data is selectively written from said selected master device to a given one of said connected slave devices, when said bus controller asserts a write data start signal to said given connected slave device.

7. The method of claim 6, wherein:

said bus controller asserts a write data start signal to said given slave device, only if said bus controller previously received a decode signal from said given connected slave device in response to a write data command.

8. The method of claim 1, wherein:

when a specified one of said connected slave devices responds to one of said commands with a retry signal, in order to indicate that the specified slave device is busy and not available to carry out the command, said selected master device will again send the command to the specified slave device.

9. The method of claim 1, wherein:

said selected master device is operated to identify a first command that cannot be sent to one of said connected slave devices until after said selected master device has received an acceptance for a previous second command, wherein said acceptance comprises an acknowledgement that a slave device has received and will carry out the previous second command.

10. The method of claim 9, wherein:

said selected master device is further operated to prevent said identified first command from being sent, until said selected master device has received said acceptance for said second previous command.

11. The method of claim 1, wherein:

data is selectively read from said connected slave devices to said master device, and said bus controller is provided with an arbiter that is operable to enable only one of said connected slave devices at a time to read data to said selected master device.

12. An apparatus comprising:

a bus controller having respective master and slave interfaces;

a plurality of slave devices respectively connected to a common slave interface of said bus controller; and

one or more master devices connected to a master interface of said bus controller, wherein a selected master device is operable to send multiple commands to selected connected slave devices in accordance with a command pipelining procedure that includes sending a first command to a connected slave device, and then sending a second command to a connected slave device before an acknowledgement for said first command has been received back by said selected master device, from the slave device to which the first command was sent.

13. The apparatus of claim 12, wherein:

each connected slave device, after receiving a command at a given time, responds to the received command a pre-specified number of clock periods after said given time.

14. The apparatus of claim 12, wherein:

each one of said connected slave devices, in sending a response to one of said commands, includes a decode signal in the response that is unique to the sending slave device.

15. The apparatus of claim 14, wherein:

data is selectively written from said selected master device to a given one of said connected slave devices, when said bus controller asserts a write data start signal to said given slave device.

16. The apparatus of claim 15, wherein:

said bus controller asserts a write data start signal to said given slave device, only if said bus controller previously received a decode signal from said given slave device in response to a write data command.

17. The apparatus of claim 12, wherein:

when a specified one of said connected slave devices responds to one of said commands with a retry signal, in order to indicate that the specified slave device is busy and not available to carry out the command, said selected master device will again send the command to the specified slave device.

18. The apparatus of claim 12, wherein:

said selected master device is operable to prevent a command from being sent to one of said connected slave devices until after said selected master device has received an acceptance for a particular previous command, wherein said acceptance comprises an acknowledgement that a slave device has received and will carry out the particular previous command.

19. The apparatus of claim 12, wherein:

data is selectively read from said connected slave devices to said master device, and said bus controller is provided with an arbiter that is operable to enable only one of said connected slave devices at a time to read data to said selected master device.

20. A computer program product in a computer readable medium for use with a bus and associated bus controller, wherein the bus controller has respective master and slave interfaces for use in selectively interconnecting master devices and slave devices, said computer program product comprising:

first instructions for connecting one or more of said master devices to one of said master interfaces of said bus controller;

second instructions for connecting each of a plurality of slave devices to the same particular one of said slave interfaces of said bus controller; and

third instructions for operating a selected connected master device to send multiple commands to selected connected slave devices in accordance with a command pipelining procedure.