| 摘要 |
PROBLEM TO BE SOLVED: To provide a microcomputer which can use a JTAG port by specific operation even after a security bit is set. SOLUTION: When an address AD2 and data DT2 are inputted from the JTAG port 11, those address AD2 and data DT2 are held in shift registers 26 and 25 respectively through TAP 24. The address AD2 is given to a flash ROM and the data DT1 in the address specified by the address AD2 are read out and outputted to a comparator 27. The data DT2 held in the shift register 25 are also outputted to the comparator 27. When the data DT1 and DT2 match each other, the output of the comparator 27 goes up to 'H' and the output of an AND 23 becomes 'L' irrelevantly to a security signal SEQ. Consequently, a switch part 12 turns on and the JTAG port 11 is connected to TAPs 13 and 14 through the switch part 12. |
