COPROCESSOR SYSTEM AND EXTERNAL MEMORY DEVICE WITH AUXILIARY OPERATION FUNCTION

摘要

PURPOSE:To improve the processing efficiency by enabling a C-CPU and an S-CPU to access an M-ROM practically simultaneously (dual phase) without increasing the memory capacity. CONSTITUTION:A gate system 10 includes an S-CPU 18 of a game machine main body 12 and a C-CPU 34 of a cartridge 14, and CPUs 18 and 34 consist of the same CPU core and have the same memory mapping. The access time of an M-ROM 22 of the cartridge 14 is shorter than the cycle time of the C-CPU 34, and the cycle time of the C-CPU 34 is shorter than that of the S-CPU 18. The period when the access from the S-CPU 18 to the M-ROM 22 is permitted by a signal SSYNC is longer than th8 access time of the M-ROM 22 and is shorter than the cycle time of the S-CPU 18. Consequently, the access from the C-CPU at to the M-ROM 22 is permitted in a margine time by the signal SSYNC.