| 摘要 |
PURPOSE:To read or modify an internal state optionally by an MPC by providing a scanning circuit which inputs the address signal from a selector, receiving the output of a scan register and an external scan address signal and selects one of them. CONSTITUTION:When a microinstruction at a microprogram control part(MPC) 10 is written in a scan register 16, an MPC mode, a scan mode, and a scan address are written in the scan register 16. When the selector 17 is switched to the internal scan address signal side in this MPC mode, the address which is set inside is inputted to the scan circuit 20 and a state value written in the flip-flop corresponding to the address is outputted to a scan-out (SOUT) termi nal. Then this scan-out value is written in a state holding register 18. Consequent ly, an optional internal state is read by the MPC 10 or altered without increas ing mutual connections between signal lines. |
