| 摘要 |
PROBLEM TO BE SOLVED: To easily apply a general purpose ICE to the debug, etc., of an ASIC 1 (application specific integrated circuit) by switching the control between control by a CPU core 2 and the control from the outside by a simple constitution, when a signal is transmitted. SOLUTION: In the control bus 10 provided between a CPU core 2 and a user circuit 3, in an address bus 11 and between data output bus 13 and data input bus 14 which are converted and connected in a unidirection, three-state buffers 8a to 8c and external terminals 7a to 7c are interposed, respectively, in order of the flowing directions of signals. When the user circuit 3 is controlled from the outside, the outputs of the three-state buffers 8a and 8b are inhibited by a bus control circuit 4, and the three-state buffer 8c switches the output/output inhibition by the control signal according to the input/output of data. |
