Boot principle: 1. Under normal circumstances, press the power button to change the PWRBT# signal from low to high (3.3V), and send out the CPWBTN# signal through the single chip microcomputer U27(AT90S 1200), shape it through U2 1(74 14), and input the KIN977 signal to I. 83977 to send PW through PIN72.

2. When booting with a password, first set it in CMOS: after booting, enter the CMOS setting, enter the integrated peripheral, and set the boot password. The power-on password will be saved in the register of 83977, and the information will be saved by the battery after power failure. When the power-on password is input, the keyboard port sends the password data to 83977, and the comparator judges whether the password is correct or not. If the password is correct, the 83977PIN69 PWRCTL signal directly outputs a low level to turn on the ATX power supply.

Note: 83,977 points are 83,977 TF and 83,977 EF, and 83,977 EF is greater than 83,977 TF.

3. The startup schematic diagram is shown in the left figure.

Second, the working principle of lock easy

The functions of 1 and Lock will block the ports of RESET, power key, keyboard and PS/2MOUSE. But CDROM and COM ports are not blocked.

2. The locking function is a safety function. You should also enter the CMOS setting options security settings and set the locking function: enable and set the security password; Meanwhile. Enter the power management settings, and set recovery via LAN and recovery via ringtone to enabled.

3. The security password is stored in 37 1 register, and the information is saved by battery power supply after shutdown. When testing the safety function, short-circuit the sleep switch, and the system will enter the sleep state. If you type any key except the password, the system will not recover.

When the security password is input, the MCU U27(AT90S 1200) receives the keyboard port data through SMBDATA and SMBCLK signals. After each data is input, the request signals KBIRQ 1 and ENIRQ 1 of U27 make the system respond to an EXTSMI system management interrupt request. Comparing the security passwords stored in 37 1 chip, if the password pair is input, the signals of SMTBTN#, RSTBTN#, PWBTN, ESMI#, CRSTBTN# and CPWBTN are turned on (usually in blocking state) and the system is restored.