1. An error detecting device for detecting an occurrence of a data error in a register for holding input data with reception of a write permission, the error detecting device comprising: an operation unit for performing a prescribed operation with each data output from a plurality of registers to be examined; a memory for storing data for comparison; a write unit for writing data obtained by the operation unit into the memory in accordance with the timing of the write permission; and a comparison unit for comparing the data for comparison stored in the memory with the data obtained by the operation unit.