Stop Mode; Low-Power Mode - Nintendo DMG-01 - Game Boy Console Manual

TM
Game Boy CPU Manual
It is not a good idea to assume the above values
will always exist. A later version GameBoy could
contain different values than these at reset.
Always set these registers on reset rather than
assume they are as above.
Please note that GameBoy internal RAM on power up
contains random data. All of the GameBoy emulators
tend to set all RAM to value $00 on entry.
Cart RAM the first time it is accessed on a real
GameBoy contains random data. It will only contain
known data if the GameBoy code initializes it to
some value.

2.7.2. Stop Mode

The STOP command halts the GameBoy processor
and screen until any button is pressed. The GB
and GBP screen goes white with a single dark
horizontal line. The GBC screen goes black.

2.7.3. Low-Power Mode

It is recommended that the HALT instruction be used
whenever possible to reduce power consumption & extend
the life of the batteries. This command stops the
system clock reducing the power consumption of both
the CPU and ROM.
The CPU will remain suspended until an interrupt
occurs at which point the interrupt is serviced and
then the instruction immediately following the HALT
by DP
2.7.1. Power Up Sequence
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