| 摘要 |
PROBLEM TO BE SOLVED: To reduce overhead of a CPU in a serial interface circuit. SOLUTION: Mirror registers 16 to 19 corresponding to registers 56 to 59 in a backup area are provided in a power off area, and the CPU parallelly accesses the mirror registers 16 to 19 through a system bus. On the other hand, when contents of the registers 56 to 59 in the backup area change, a change notification circuit 63 inverts the level of serial read data SRD and notifies the power off area of the inverted level. A control block 15 makes a serial read request to the backup area side and stores the serial read data SRD transferred from the backup area in the mirror registers 16 to 19 when update of the registers is detected. COPYRIGHT: (C)2007,JPO&INPIT
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