Transaction scheduling for a bus system

Abstract

A method of and apparatus for communicating data using a hub. The method includes the step of buffering a single transfer request received at a hub during a transaction between the hub and a host controller, where the single transfer request is to be performed between the hub and an agent to generate a result. The method then includes the step of determining whether a transfer inquiry received at the hub from the host controller corresponds to the result.

1 . A method for communicating data using a hub, the method comprising: 
 buffering a single transfer request received at a hub during a transaction between the hub and a host controller;    wherein the single transfer request is to be performed between the hub and an agent to generate a result; and    determining whether a transfer inquiry received at the hub from the host controller corresponds to the result.    
     
     
         2 . The method of  claim 1 , wherein the single transfer request is received at a first data rate or a first protocol.  
     
     
         3 . The method of  claim 1 , wherein the single transfer request is performed at a second data rate or a second protocol.  
     
     
         4 . The method of  claim 3 , wherein 
 the hub includes storage for buffering transfer requests, and    at any instant in time transfer requests buffered in the storage take up an aggregate storage space that is less than an information capacity of three communication frames between the hub and the agent.    
     
     
         5 . The method of  claim 3 , wherein 
 at any instant in time transfer requests buffered in the storage take up an aggregate storage space that is less than an information capacity of a communication frame between the hub and the agent.    
     
     
         6 . The method of  claim 1 , wherein the single transfer request is associated with a time stamp and the step of performing includes, 
 comparing the time stamp with a time indication, and    performing the single transfer request when the time stamp is within a predetermined time range relative to the time indication.    
     
     
         7 . The method of  claim 1 , wherein the single transfer request is associated with a time stamp and the step of performing includes, 
 comparing the time stamp with a time indication, and    preventing the host controller from performing the single transfer request when the time stamp is outside a predetermined time range relative to the time indication.    
     
     
         8 . The method of  claim 1 , wherein the step of buffering includes, 
 storing a transaction record corresponding to the single transfer request.    
     
     
         9 . The method of  claim 6 , wherein the step of buffering includes, 
 setting a status field for the single transfer request to pending.    
     
     
         10 . The method of  claim 7 , wherein the step of buffering includes, 
 defining a data reference field if the single transfer request requires data to be received at the hub from the agent or sent to the agent.    
     
     
         11 . The method of  claim 1 , further comprising: 
 sending from the hub to the host controller a response based on the result when the result corresponds to information received in the transfer inquiry.    
     
     
         12 . The method of  claim 1 , wherein the step of determining includes, 
 comparing a transaction record corresponding to the single transfer request with information received in the transfer inquiry.    
     
     
         13 . An input/output device for communicating data, comprising: 
 a memory adapted to buffer a single transfer request received during a transaction between a host controller and the device;    a hub controller that performs the single transfer request between the device and an agent to generate a result;    wherein the device receives a transfer inquiry from the host controller; and    a control unit that determines whether the transfer inquiry corresponds to the result.    
     
     
         14 . The device of  claim 13 , wherein the single transfer request is received at a first communication speed or a first protocol.  
     
     
         15 . The device of  claim 13 , wherein the single transfer request is performed at a second communication speed or a second protocol.  
     
     
         16 . The device of  claim 13 , wherein 
 at any instant in time transfer requests buffered in the memory take up an aggregate storage space that is less than the information capacity of a communication frame between the hub controller and the agent.    
     
     
         17 . The device of  claim 16 , wherein the aggregate storage space is less than three-fourths of the information capacity of the communication frame between the hub controller and the agent.  
     
     
         18 . The device of  claim 13 , wherein the memory has a plurality of stages including a first stage storing a first transfer request and an adjacent second transfer request, an interval during which transfer requests are not received at the hub separates receipt of the first transfer request and the second transfer request, and the hub controller performs the first transfer request and the second transfer request.  
     
     
         19 . The device of  claim 18 , wherein performance of the first transfer request by the hub controller and performance of the second transfer request by the hub controller is divided by a delay less than the interval.  
     
     
         20 . The device of  claim 16 , wherein the memory stores a transaction record corresponding to the single transfer request.  
     
     
         21 . The device of  claim 16 , wherein the memory stores a status field corresponding to the single transfer request and the status field is indicative of a pending status.  
     
     
         22 . The device of  claim 16 , wherein the memory stores a transaction record at an address indicative of a pending status.  
     
     
         23 . The device of  claim 16 , wherein the memory stores a data reference when the single transfer request requires data to be received at the hub from the agent or sent to the agent.  
     
     
         24 . The device of  claim 16 , wherein the hub controller sends from the device to the host a response based on the result.  
     
     
         23 - 46 . (Cancelled)