7.1 Device Status

For each device, the ball tracker maintains the following state information:

• The maximum number of balls it can hold. This is a constant that depends on the number of counting switches in the device.
• The current number of balls it contains
• The previous number of balls it contained earlier
• The desired number of balls that game logic wants it to have
• Whether or not it is in the process of trying to release a ball

The desired count is crucial to understanding the module's behavior. Whenever the device has more balls than desired, the ball tracker will initiate one or more releases to try to bring the count down to the desired number. Otherwise, any balls that enter the device are kept there; this is used to implement ball locks.

Software requests to kick a ball are always done by manipulating the desired count. The device module has complete control over the actual release solenoid.

The trough device is the only device which normally desires to keep any balls. Playfield devices generally desire zero balls unless a lock has been enabled.

Device switches must be declared as edge switches, which invoke the event handler on both open and close transitions. The tracker simply updates the current count on either type of transition.