| 摘要 |
PURPOSE:To detect the presence of an extended interface circuit and its type, by providing a detecting circuit to a system extending system of a microcomputer in order to read out the information on the extended interface circuit. CONSTITUTION:Both address and data for selection of extended interface circuits 18-20 are written to an extended interface detecting circuit 13 from a CPU8 via an address bus 11 and a data bus 12. The address is decoded by the circuit 13, and just one of extended interface detecting signals 14-16 is validated. The CPU8 switches successively the signals 14-16 and then reads out these signals. Thus it is possible to detect the presence of a connected extended interface circuit and its type. This improves the efficiency for system extension. |
