Split transaction protocol for a bus system

Abstract

A method of and apparatus for communicating between a host and an agent. The method includes the step of performing a first transaction between a host controller and a hub. The hub is operable to perform a single transaction with an agent based on the first transaction. The method then includes the step of performing a second transaction between the host controller and the hub. The second transaction is based on the single transaction.

What is claim is: 
     
         1 . A device comprising:
 a camera;   a controller hub coupled to the camera, wherein the controller hub is to:   receive a start split transaction at a high speed to indicate a beginning of a transfer;   send a token to the camera at a low-speed, wherein the token includes a transfer type and a data rate identification; and   receive data from the camera, wherein the controller hub is to include a buffer to buffer the data received from the camera until after a speed shift from the low-speed to the high-speed is performed.   
     
     
         2 . The device of  claim 1 , wherein the split transaction includes a first transaction and a second transaction. 
     
     
         3 . The device of  claim 2 , wherein the first transaction is performed at a first communication speed or in accordance with a first protocol, and the second transaction is performed at a second communication speed or in accordance with a second protocol. 
     
     
         4 . The device of  claim 1 , wherein a second transaction is to be initiated while the buffer is to buffer the data. 
     
     
         5 . The device of  claim 1 , wherein the controller hub is further coupled to a host controller that is to transmit the split transaction, and wherein the host controller is to provide an acknowledgement to the controller hub in response to the buffered data. 
     
     
         6 . The device of  claim 1 , wherein the speed shift comprises a conversion from the low-speed to the high-speed. 
     
     
         7 . The device of  claim 1 , wherein the high speed is a greater speed than the low speed. 
     
     
         8 . A system comprising:
 a game machine including a plurality of digital devices to be in communication, wherein a particular digital device of the plurality of digital devices comprises a camera and a controller hub, the controller hub comprising:   an upstream port to receive a start split transaction at a high speed and data; and   a buffer to buffer the data to be received at the upstream port until after a speed shift from the high speed to a low-speed, wherein a token is sent to the camera at the low-speed and the token includes a transfer type and a data rate identification.   
     
     
         9 . The system of  claim 8 , wherein the upstream port is to operate in accordance with a first protocol, and the downstream port is to operate in accordance with a second protocol. 
     
     
         10 . The system of  claim 8 , wherein a second transaction is initiated while the data is buffered. 
     
     
         11 . The system of  claim 8 , wherein the buffer is to store the data that is received at the low-speed. 
     
     
         12 . The system of  claim 8 , wherein the controller hub is to perform a first transaction in accordance with a first protocol, and a second transaction in accordance with a second protocol. 
     
     
         13 . The system of  claim 8 , further comprising a display. 
     
     
         14 . A controller hub comprising:
 an upstream port that is capable to send and receive a start split transaction and to operate at a high speed, wherein the start split transaction is to indicate a beginning of a transfer;   a downstream port that is capable to transmit an in token, to receive an out token, and to receive data, wherein the downstream port that is capable to operate at a low-speed, wherein the in token includes a transfer type and a data rate identification; and   a buffer to buffer the data from the upstream port and the downstream port and perform a speed conversion from the low-speed to the high-speed.   
     
     
         15 . The controller hub of  claim 14 , wherein the upstream port is to operate in accordance with a first protocol, and the downstream port is to operate in accordance with a second protocol. 
     
     
         16 . The controller hub of  claim 14 , wherein a second transaction is initiated while the data is buffered. 
     
     
         17 . The controller hub of  claim 14 , wherein the controller hub is coupled with a game machine. 
     
     
         18 . The controller hub of  claim 14 , wherein the controller hub is coupled with a display. 
     
     
         19 . The controller hub of  claim 14 , wherein the upstream port is to operate in accordance with a first protocol, and the downstream port is to operate in accordance with a second protocol. 
     
     
         20 . The controller hub of  claim 14 , wherein the split transaction includes a first transaction and a second transaction.