| 摘要 |
PURPOSE:To extract the contents of an RAM to the outside by use of a small number of terminal pins, by arranging a register and a controller to a chip of a microcomputer containing an RAM and at the same time writing the prescribed data same as the RAM into the register. CONSTITUTION:A memory region 14a into which a data to monitor the working of a CPU12 is written, a register 22 that writes a data same as the region 14a plus a control circuit 24 that controls the register 22 are included in an RAM14 of a semiconductor chip 10. The CPU12, when writing the result of operation, etc. into the region 14a, writes the data also into the register 22 via the circuit 24. The register 22 is always replaced and holds the same contents as the region 14a. When the data is sent to outside, the CPU12 gives a DMA command to the circuit 24, transfers the contents of the register 22 to a transmitting register 20 and reads successively the contents of the register 22 with the same clock as that used for a serial I/O18 to transmit the contents in series to outside. The data can be transmitted quickly with just a single terminal pin and with a DMA command given to the circuit 24 from the CPU12. |
