AGB allows input with the L and R buttons, as well as with the START and SELECT buttons, Control Pad, and A and B buttons.
The status of each of these buttons can be checked by reading the individual bits of Register P1.
When an interrupt is performed for key input, this register enables a target key combination or condition for the interrupt to be specified.
Specifies interrupt generation conditions when the interrupt enable request flag is true.
The conditions for buttons selected with the key interrupt specification flag can be selected as follows.
1. Logical Addition (OR) Operation
The conditions for interrupt request generation occur when there is input for any of the buttons specified as interrupts.
2. Logical Multiplication (AND) Operation
The conditions for interrupt request generation occur when there is simultaneous input for all of the keys specified as interrupt keys.