Method and apparatus for attaching multiple slave devices to a single bus controller interface while supporting command pipelining

• US 7,865,644 B2
• Filed: 10/30/2007
• Issued: 01/04/2011
• Est. Priority Date: 10/30/2007
• Status: Expired due to Fees

• Current Assignee: LinkedIn Corporation (Microsoft Corporation)
• Original Assignee: International Business Machines Corporation
• Inventors: Srinivasan, Prasanna, Nicholas, Richard, Drerup, Bernard Charles
• Primary Examiner(s): Rinehart; Mark
• Assistant Examiner(s): Patel; Nimesh G
• Application Number:
  US11/927,911
• Publication Number:
  US 20090113097A1
• Time in Patent Office: 1,162 Days
• Field of Search: 710/110, 710/306
• 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 one of said slave devices to the same particular one of said slave interfaces of said bus controller;

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

wherein signals from said particular one of said slave interfaces are multi-dropped to each one of said slave devices, and further wherein signals from each one of said slave devices responsive to said commands are received by a logic OR gate that generates an output signal that is received by the bus controller; and

wherein each connected slave device responds to each received command at a same fixed number of clock cycles after each received command, wherein responses from each connected slave device always occur at said fixed number.

2. The method of claim 1, wherein:

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

3. The method of claim 1, wherein:

each one of said connected slave devices, in responding to one of said commands, generates a response signal and generates a decode signal, which is separate from the response signal, and wherein the decode signal is unique to the sending slave device.

4. The method of claim 3, 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.

5. The method of claim 4, wherein:

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

6. 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 bus controller continually sends said one of said commands while said specified one of said connected slave devices remains busy.

7. 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.

8. The method of claim 7, 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.

9. 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.

10. 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;

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;

wherein signals from said common slave interface are multi-dropped to each one of said plurality of slave devices, and further wherein signals from each one of said plurality of slave devices responsive to said commands are received by a logic OR gate that generates an output signal that is received by the bus controller; and

wherein each connected slave device responds to each received command at a same fixed number of clock cycles after each received command, wherein responses from each connected slave device always occur at said fixed number.

11. The apparatus of claim 10, wherein:

each one of said connected slave devices, in responding to one of said commands, generates a response signal and generates a decode signal, which is separate from the response signal, and wherein the decode signal is unique to the sending slave device.

12. The apparatus of claim 11, 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.

13. The apparatus of claim 12, wherein:

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

14. The apparatus of claim 10, 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 bus controller continually sends said one of said commands while said specified one of said connected slave devices remains busy.

15. The apparatus of claim 10, 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.

16. The apparatus of claim 10, 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.

17. 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 one of said slave devices to the same particular one of said slave interfaces of said bus controller;

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;

wherein signals from said particular one of said slave interfaces are multi-dropped to each one of said slave devices, and further wherein signals from each one of said slave devices responsive to said commands are received by a logic OR gate that generates an output signal that is received by the bus controller; and

wherein each connected slave device responds to each received command at a same fixed number of clock cycles after each received command, wherein responses from each connected slave device always occur at said fixed number.