| 摘要 |
<p>PURPOSE:To set exactly a short time value, as well by supplying a reference clock to a direct memory access (DMA) circuit at the time when a data transfer is not executed, making it execute a DMA operation, and obtaining an output showing a necessary elapsed time when a transfer operation of a prescribed byte number is ended. CONSTITUTION:A micro-processor (MPU) 13 sets an initial value of an address to an address generating circuit 22, and also sets a transfer byte number to a transfer byte number counter 21. When a time counting start signal is applied and a transfer request signal is received, a bus controlling circuit 23 sends a bus occupancy request signal to the MPU 13, and in accordance with a using state of a bus 16, an approval signal is received by the bus controlling circuit. A transfer address is set to a memory 14 and a data is transferred to the memory 14 from a peripheral circuit 15. When the data transfer is ended, the operation as a timer is ended. This data transfer is executed by a prescribed clock period, and a desired timer value can be set by setting a transfer byte number.</p> |
