To open the treasury, the user must enter a serial binary password of 6 bits. Each bit is
entered with a manual pulse at the input CLOCK. If the entered password is correct, the
output LOCK is logic 1 and the treasury is open (you may use a green light to indicate the
action). The treasury will remain open if the value at input DATA is still 1, but if the user
enters a 0 at input DATA, then the treasury will close. Don’t forget the pulse to enter the
While if the entered password is wrong, then the output ALARM is logic 1 (informing the
police) and LOCK is logic 0 (the treasury is not open). You may use an orange light to
indicate the police and red light to indicate that the treasury is not open.
The user can change the password by pressing input PR, but he/she must enter the old
password, followed by the 6-bit new password (12 bits total). If the user enters the correct
old password and a 6-bit new password, the output PCh will be logic 1. The user has 2
wrong attempts to change the password, otherwise the output ALARM will become 1.
If the output ALARM is logic 1, it would never become 0 until the user presses the input
RESET followed by the correct password.