Generating multiple traffic classes on a PCI Express fabric from PCI devices

Abstract

A system having a PCI Express fabric and PCI devices connected thereto transmits data from the PCI devices having PCI Express traffic classes assigned. A PCI Express to PCI bridge assigns a predetermined address to the grant line for each PCI device coupled to the PCI bus and stores this address along with the data from the PCI device in the PCI transaction queues. When the data is transmitted along the PCI Express fabric, or when it is processed within the PCI Express to PCI bridge, the address assigned to the respective grant line becomes the PCI Express traffic class for that data. This enables the commands from one device to be processed irrespective of commands from other PCI devices on the PCI bus.

1 . A PCI Express to PCI bridge comprising: 
 a PCI bus interface couplable to a PCI bus;    a PCI bus arbiter coupled to the PCI bus interface and having request/grant lines for PCI devices to be connected to the PCI bus;    PCI transaction queues are coupled to the PCI bus interface for receiving PCI transactions;    a PCI Express interface coupled to the PCI transaction queues and to a PCI Express output port; wherein the PCI bus arbiter assigns a PCI Express traffic class code to data received from a PCI device, the traffic class code being different for each PCI device connected to the PCI bus.    
   
   
       2 . The bridge of  claim 1  wherein the PCI Express traffic code assigned to data from the PCI device is related to the address of the request/grant lines for that device.  
   
   
       3 . The bridge of  claim 1  wherein the PCI Express traffic code comprises 3 bits.  
   
   
       4 . The bridge of  claim 2  wherein the PCI Express traffic code comprises 3 bits.  
   
   
       5 . A method of operating a PCI Express to PCI bridge comprising: 
 receiving a request for access to a PCI bus from a PCI device coupled to the PCI bus;    generating a grant to the PCI device for access to the bus;    storing data received from the PCI device in a PCI transaction queue, the data being stored with a PCI Express traffic class corresponding only to that PCI device.    
   
   
       6 . The method of  claim 5  wherein the PCI Express traffic code assigned to data from the PCI device is related to the address of the request/grant lines for that device.  
   
   
       7 . The method of  claim 5  wherein the PCI Express traffic class comprises 3 bits.  
   
   
       8 . The method of  claim 6  wherein the PCI Express traffic class comprises 3 bits.  
   
   
       9 . A method of transmitting data generated by PCI device on a PCI Express fabric comprising: 
 receiving data from a PCI device;    storing the data with a predetermined PCI Express traffic class code corresponding to the PCI device; and    transmitting the data and the traffic code on the PCI Express fabric.    
   
   
       10 . The method of  claim 9  wherein the PCI Express traffic code is contained in the header of a packet transmitted on the PCI Express fabric.  
   
   
       11 . The method of  claim 9  wherein the PCI Express traffic class comprises 3 bits.  
   
   
       12 . The method of  claim 10  wherein the PCI Express traffic class comprises 3 bits.  
   
   
       13 . The method of  claim 9  wherein the PCI Express traffic code assigned to data from the PCI device is related to the address of the request/grant lines for that device.  
   
   
       14 . The method of  claim 10  wherein the PCI Express traffic code assigned to data from the PCI device is related to the address of the request/grant lines for that device.  
   
   
       15 . The method of  claim 13  wherein the PCI Express traffic class comprises 3 bits.  
   
   
       16 . The method of  claim 14  wherein the PCI Express traffic class comprises 3 bits.