| 摘要 |
PURPOSE:To initialize easily a comparatively large memory area, and to reduce burden of software by providing a data transfer word number controlling circuit and an initial value setting circuit, on a direct memory access circuit. CONSTITUTION:A data transfer word number controlling circuit 11 provided on a direct memory access controlling circuit 10 masks upper (N-n) bits of a data transfer word number TC setting bit and delivers them to a data transfer word number latching circuit 8. That is to say, when the designated TC is <=2<n>, they are delivered to the circuit 8 by subtracting 2<n> from the TC. Also, when at least 1-bit among the upper (N-n) bits is ''1'', it is informed as an initializing request signal 13 to an initializing value setting circuit 12. That is to say, when a memory is initialized in software, the head address of the memory to be initialized is used as a data transfer start address, and a value which has added 2<n> to the number of words of the memory to be initialized is made the number of data transfer words. In this way, a comparatively large memory area is initialized, and burden of software can be reduced. |
