Power-Down Functions

# 16 Power-Down Functions

## 16.1 Stop Function

### Stop Function Summary

During periods when the LCD display is not done and CPU processing is not considered essential you can reduce power consumption greatly if used efficiently.

The content of each type of RAM are maintained.

### Implementing Stop

1) Implemention of Stop Mode

AGB is placed in stop mode by executing the system call [SWI <3>] instruction (Stop( )).

2) Canceling Stop Mode

If the appropriate interrupts are enabled in the interrupt enable register IE, for each interrupt request for the key, Game Pak, and SIO (general purpose communication mode), Stop is cancelled.

[Note]

Canceling stop status requires a brief wait until the system clock stabilizes.

### System Working Status in Stop Mode

The working status of each block of the AGB system during a stop is shown in the following table.

Block | Working | Status
AGB-CPU | X | Wait status resulting from wait signal
LPU | X | Stopped because no clock provided*
Sound | X | Stopped*
Timer | X | Stopped
Serial Communication | X | Stopped
Key | X | Stopped
System Clock | X | Stopped
Infrared Communication | X | Stopped

*[Note]

Enter Stop Mode after turning the LCD display OFF because LPU stops.

Sound stops in Stop Mode, therefore noise may be heard.

## 16.2 Halt Function

### Halt Function Summary

During periods when CPU processing is not considered essential you can reduce power consumption if used efficiently.

### Halt Transition Method

1. Transition to Halt Mode

AGB is placed in halt mode by executing the system call [SWI <2> instruction (Halt( )).

AGB enters Halt status.

2. Cancel Halt Mode

Halt is canceled when the interrupt enable register IE's corresponding flag is set with any type of interrupt request.

### System Working Status in Halt Mode

The working status of each block of the AGB system during a semi-stop is shown in the following table.

Block | Working | Status
AGB-CPU | X | Wait status resulting from wait signal
LPU | O | Normal operation
Sound | O | Normal operation
Timer | O | Normal operation
Serial Communication | O | Normal operation
Key | O | Normal operation
System Clock | O | Normal operation