1. A decoding circuit for decompressing lossless-encoded compressed data, comprising: a separator, arranged to separate the compressed data into a first command that requires memory access and a second command that requires no memory access, by referring to a command table; a decoder, arranged to request memory read of decompressed data necessary for decompression of the first command, decode the first command based on the decompressed data, and request memory write of decompressed data obtained by decoding; and a memory controller, arranged to control read and write of a cache memory and a line memory and execute memory read and memory write corresponding to a request from said decoder.