Apparatus and method of partially transferring data through bus and bus master control device

Abstract

A method of transferring data through a bus includes the steps of: occupying the bus by a first device serving as a bus master; transferring a first predetermined number of data items of all data items to be transferred while the first device is occupying the bus; determining if the first predetermined number of data items have been transferred; determining if the first device should release the bus based on whether or not there is a request from a second device after it is determined that the first predetermined number of data items have been transferred; and releasing the bus by the first deice when it is determined that the first device should release the bus.

1. A method of transferring data through a bus, comprising the steps of:
 continuously occupying the bus by a first device serving as a bus master, said first device continuously occupying the bus for a predetermined period of time;  
 transferring a first predetermined number of data items of all data items to be transferred while the first device is occupying the bus, the first predetermined number of data items transferring without interruption based on said predetermined period time;  
 determining if the first predetermined number of data items have transferred;  
 repeatedly transferring by said first device additional sets of a predetermined number of data items of all data items to be transferred while said first device occupies said bus despite a request from a second device for access to said bus, 
 determining if the first device should release the bus based on whether or not there is a request from a  the second device after it is determined that he first predetermined number of data items of all data items to be transferred have been transferred; and  
 releasing the bus by the first device when it is determined that the first device should release the bus.  
 
     
     
       2. A method of transferring data through a bus according to  claim 1 , further comprising the steps of:
 occupying the bus by the second device serving as the bus master after the first device releases the bus;  
 releasing the bus by the second device after the second device complete access to the bus;  
 occupying the bus again by the first device after the second device releases the bus; and  
 transferring a second predetermined number of data items subsequent to the first predetermined number of the data items which have been transferred while the first device is occupying the bus again.  
 
     
     
       3. A method of transferring data through a bus according to  claim 1 , further comprising the step of, when it is determined that the first device should not release the bus, transferring by the first device a second predetermined number of data items subsequent to the first predetermined number of the data items which have been transferred while the first device continues to occupy the bus. 
     
     
       4. A method of transferring data through a bus according to  claim 1 , further comprising the steps of:
 determining if all the data items to be transferred have been transferred; and  
 releasing the bus after it is determined that all the data items to be transferred have been transferred.  
 
     
     
       5. A method of transferring data through a bus according to  claim 1 , wherein:
 the first device is a DMA controller; and  
 the second device is a CPU.  
 
     
     
       6. A master control device for controlling an operation of a bus master for transferring data through a bus, the device comprising:
 bus occupation request means for outputting a signal requesting to occupy the bus in response to a data transfer request;  
 data transfer means for transferring a first predetermined number of data items of all data items to be transferred while the bus master is continuously occupying the bus for a predetermined period of time, said data transfer means configured to transfer said first predetermined number of data items of all data items to be transferred without interruption based on said predetermined period of time;  
 first determination means for determining if the first predetermined number of data items have been transferred;  
 bus release instruction means for outputting a signal instructing said bus master to release the bus based on whether or not there is a request from a first device after it is determined that the first predetermined number of data items have been transferred; and  
 bus release means for releasing the bus by the bus master when said bus master release instruction means outputs said signal instructing said bus master to release the bus,  
   wherein the data transfer means comprises a first counter for counting a number of data items which have been transferred out of the first predetermined number of data items, and a second counter for counting a number of data items which have been transferred out of all the data items to be transferred; and the first determination means determines if the first predetermined number of data items have been transferred based on an output from the first counter,    
   said data transfer means further comprising a second determination means for determining if all the data items to be transferred have been transferred based on an output from the second counter.    
 
     
     
       7. A bus master control device according to  claim 6 , wherein:
 the bus occupation request means outputs again the signal requesting to occupy the bus after the bus release instruction means outputs the signal instructing to release the bus; and  
 the data transfer means transfers a second predetermined number of data items subsequent to the first predetermined number of the data items which have been transferred while the bus master is occupying the bus again.  
 
     
     
       8. A bus master control device according to  claim 6 , wherein the bus release instruction means outputs the signal instructing to release the bus after all the data items to be transferred have been transferred. 
     
     
       9. A bus master control device according to  claim 6 , wherein:
 the data transfer means comprises a first counter for counting a number of data items which have been transferred out of the first predetermined number of data items, and    the first determination means determines if the first predetermined number of data items have been transferred based on an output from the first counter.    
     
     
       10. A bus master control device according to  claim 9 , the data transfer means comprising:
 a second counter for counting a number of data items which have been transferred out of all the data items to be transferred; and    second determination means for determining if all the data items to be transferred have been transferred based on an output from the second counter.    
     
     
       11. A method of transferring data through a bus, comprising the steps of:
   continuously occupying the bus by a first device serving as a bus master, said first device continuously occupying the bus for a period of time for transferring a first predetermined number of data items of all data items to be transferred;        transferring said first predetermined number of data items while the first device is occupying the bus, the first predetermined number of data items transferring without interruption during said period by a second device;        determining if said first predetermined number of data items have been transferred;        determining if the bus should be occupied by said second device based on whether or not there is a request from said second device; and        occupying the bus by said second device when it is determined that the bus should be occupied by said second device,        repeatedly transferring by said first device additional sets of a predetermined number of data items of all data items to be transferred while said first device occupied said bus despite a request from said second device for access to said bus,        wherein said interruption corresponds to a request for occupying said bus by said second device.     
     
     
       12. A method of transferring data through a bus according to  claim 11 , further comprising the steps of:
   occupying the bus by the second device serving as the bus master after the first device releases the bus;        releasing the bus by the second device after the second device completes access to the bus;        occupying the bus again by the first device after the second device releases the bus; and        transferring a second predetermined number of data items subsequent to the first predetermined number of data items which have been transferred while the first device is occupying the bus again.     
     
     
       13. A method of transferring data through a bus according to  claim 11 , further comprising the steps of:
   determining if all data items to be transferred have been transferred; and        releasing the bus after it is determined that all the data items to be transferred have been transferred.     
     
     
       14. A method of transferring data through a bus according to  claim 11 , wherein:
   the first device is a DMA controller; and        the second device is a CPU.     
     
     
       15. A master control device for controlling an operation of a bus master for transferring data through a bus, the device comprising:
   bus occupation request means for outputting a signal requesting to occupy the bus in response to a data transfer request;        data transfer means for transferring a first predetermined number of data items of all data items to be transferred while the bus master is continuously occupying the bus for a period of time necessary for transferring said first predetermined number of data items, said data transfer means configured to transfer said first predetermined number of data items of all data items to be transferred without interruption;        first determination means for determining if the first predetermined number of data items have been transferred;        bus release instruction means for outputting a signal instructing said bus master to release the bus based on whether or not there is a request from a second device after it is determined that the first predetermined number of data items have been transferred; and        bus release means for releasing the bus by the bus master when said bus master release instruction means outputs said signal instructing said bus master to release the bus,        wherein the data transfer means comprises a first counter for counting a number of data items which have been transferred out of the first predetermined number of data items, and a second counter for counting a number of data items which have been transferred out of all the data items to be transferred; and the first determination means determines if the first predetermined number of data items have been transferred based on an output from the first counter,        said data transfer means further comprising a second determination means for determining if all the data items to be transferred have been transferred based on an output from the second counter.     
     
     
       16. A bus master control device according to  claim 15 , wherein:
   the bus occupation request means outputs again the signal requesting to occupy the bus after the bus release instruction means outputs the signal instructing to release the bus; and        the data transfer means transfers a second predetermined number of data items subsequent to the first predetermined number of data items which have been transferred while the bus master is occupying the bus again.     
     
     
       17. A bus master control device according to  claim 15 , wherein the bus release instruction means outputs the signal instructing to release the bus after all the data items to be transferred have been transferred. 
     
     
       18. The method of  claim 11 , wherein said predetermined number is on the same page as in the page mode of DRAM. 
     
     
       19. A method of transferring data through a bus, said method comprising the steps of:
   continuously occupying the bus by a first device serving as a bus master, said first device continuously occupying the bus for a period of transferring a first predetermined number of data items to be transferred;        transferring said first predetermined number of data items of all data items to be transferred while the first device occupies the bus the first predetermined number of data items being transferred despite a request from a second device;        determining if the first predetermined number of data items have been transferred;        negating a request from the first device for bus access so as to grant the second device bus access, if the first predetermined number of data items have been transferred;        reasserting a request for bus access from the first device; and        repeatedly transferring by said first device additional sets of a predetermined number of data items while said first device occupies said bus.     
     
     
       20. The method of  claim 19 , wherein said certain number is on the same page as in the page mode of DRAM.