| 摘要 |
PURPOSE:To secure the optimum external and internal memory accesses and to increase the degree of freedom for the external memory, by providing a holding circuit to the main body of an electronic device and the external memory respectively and applying the wait to a CPU according to the comparison/selection results of the outputs of those holding circuits. CONSTITUTION:Only the main body 3 of an electronic device is used, and the set signal which is supplied to a comparator 305 from a holding circuit 402 does not exist when no auxiliary memory 4 is connected. Thus the value of the set signal is set at ''0''. Therefore the wait is applied to a CPU301 for a period of time corresponding to the set value output of a holding circuit 304 when the CPU301 accesses to an internal memory 302. With connection fo the memory 4, the comparator 305 compares the set value output of the circuit 304 with that of the circuit 402 when the CPU301 gives an access to the memory 302 or an external memeory 401. Then the wait is applied to the CPU301 for a period equivalent to the larger one of both set value outputs. |
