Semiconductor device, data processing system, and semiconductor device control method

Abstract

Bus/memory bandwidth consumption caused by reading of auxiliary information not included in compressed data is reduced. A memory stores compressed data and auxiliary information used to read the compressed data. A semiconductor device includes a cache in which auxiliary information stored in the memory is stored, a control unit which, when a read request for reading compressed data stored in the memory is received, reads from the cache auxiliary information about the compressed data, if stored in the cache, or reads the auxiliary information about the compressed data, if not stored in the cache, from the memory and stores the auxiliary information about the compressed data in the cache, and which reads the compressed data from the memory using the auxiliary information about the compressed data, and an expansion unit to expand the compressed data read from the memory.

1 - 19 . (canceled) 
     
     
         20 . A semiconductor device comprising:
 a control unit configured to read compressed data stored in a memory in response to a read request for reading the compressed data from the memory, the read request including an address of data before compression; and   a cache configured to store auxiliary information indicating a data length of the compressed data, the auxiliary information being stored in the memory together with the compressed data,   wherein the compressed data is generated by compressing the data before compression in units of a predetermined data size, and is stored in a location of the memory specified by the address of the data before compression, and   wherein, when reading the compressed data stored in the memory in response to the read request, the control unit:
 if the auxiliary information about the compressed data to be read is stored in the cache, reads from the cache the auxiliary information about the compressed data to be read, and reads from the memory the compressed data using the address included in the read request and the auxiliary information read from the cache, 
 if the auxiliary information about the compressed data to be read is not stored in the cache, reads from the memory the auxiliary information about the compressed data to be read, stores in the cache the auxiliary information read from the memory, and reads from the memory the compressed data using the address included in the read request and the auxiliary information read from the memory. 
   
     
     
         21 . The semiconductor device according to  claim 20 , wherein, when reading from the memory the auxiliary information about the compressed data to be read, the control unit reads from the memory auxiliary information of a predetermined unit including the auxiliary information about the compressed data to be read, and stores in the cache the auxiliary information of the predetermined units read from the memory. 
     
     
         22 . The semiconductor device according to  claim 21 ,
 wherein, when reading from the memory and storing in the cache the auxiliary information of the predetermined unit, the control unit reads, as advance reading, from the memory auxiliary information of a next predetermined unit, and stores in the cache the auxiliary information of the next predetermined unit read from the memory, and   wherein the auxiliary information of the predetermined unit and the auxiliary information of the next predetermined unit being contiguous in address.   
     
     
         23 . The semiconductor device according to  claim 22 , wherein the control unit determines whether to read the auxiliary information of the next predetermined unit based on a capacity of the cache. 
     
     
         24 . The semiconductor device according to  claim 20 , wherein the control unit holds management information indicating the auxiliary information stored in the cache, and determines whether the auxiliary information about the compressed data to be read is stored in the cache based on the management information. 
     
     
         25 . The semiconductor device according to  claim 20 , wherein an order of storing the compressed data in the memory and an order of storing auxiliary information about the compressed data in the memory are identical. 
     
     
         26 . The semiconductor device according to  claim 20 , further comprising an expansion unit configured to expand the compressed data read from the memory. 
     
     
         27 . The semiconductor device according to  claim 20 , further comprising an operation unit configured to output the read request. 
     
     
         28 . A data processing system comprising:
 the semiconductor device according to  claim 20 , and   the memory configured to store the compressed data and the auxiliary information.   
     
     
         29 . A control method of the semiconductor device for reading compressed data stored in a memory using auxiliary information, wherein the semiconductor device comprises a cache, the auxiliary information indicates a data length of the compressed data and is stored in the memory together with the compressed data, the compressed data is generated by compressing data before compression in units of a predetermined data size and is stored in a location of the memory specified by an address of the data before compression, the control method comprising:
 generating a read request for reading the compressed data from the memory, the read request including the address of the data before compression;   determining whether the auxiliary information about the compressed data to be read is stored in the cache in response to the read request;   if the auxiliary information about the compressed data to be read is stored in the cache,
 reading from the cache the auxiliary information about the compressed data to be read; 
 reading from the memory the compressed data using the address included in the read request and the auxiliary information read from the cache; 
   if the auxiliary information about the compressed data to be read is not stored in the cache,
 reading from the memory the auxiliary information about the compressed data to be read; 
 storing in the cache the auxiliary information read from the memory; and 
 reading from the memory the compressed data using the address included in the read request and the auxiliary information read from the memory. 
   
     
     
         30 . The control method of the semiconductor device according to  claim 29 ,
 wherein the reading from the memory the auxiliary information about the compressed data to be read comprises reading from the memory auxiliary information of a predetermined unit which includes the auxiliary information about the compressed data to be read, and   wherein the storing in the cache the auxiliary information read from the memory comprises storing in the cache the auxiliary information of the predetermined units read from the memory.   
     
     
         31 . The control method of the semiconductor device according to  claim 30 , further comprising:
 reading, as advance reading, from the memory auxiliary information of a next predetermined unit; and   storing in the cache the auxiliary information of the next predetermined unit read from the memory,   wherein the auxiliary information of the predetermined unit and the auxiliary information of the next predetermined unit are contiguous in address.   
     
     
         32 . The control method of the semiconductor device according to  claim 29 , wherein the determining comprises:
 holding management information indicating the auxiliary information stored in the cache; and   determining whether the auxiliary information about the compressed data to be read is stored in the cache based on the management information.   
     
     
         33 . The control method of the semiconductor device according to  claim 29 , further comprising expanding the compressed data read from the memory.