Nintendo GAME BOY Programming Manual page 44

Game Boy Programming Manual
2.6.3.10 Usage Notes
When programming use of the infrared port, please note the following.
! When transmitting more than 256 bytes of data, ensure that the receiver
keeps track of which packet number is being received. When a
communication error (status not returned even though data was received)
is generated, the sender will re-send the data, and the receiver may lose
track of the packet number (see note 1 of previous section).
! The sender is prone to entering an endless loop when the packet
signifying transmission completion is received. Therefore, the receiver
should remain in receive status for approximately 300 µs after returning
the status (see note 2 of previous section).
! Depending on the power reserve of the battery, infrared communication
may cause a sudden drop in battery voltage and a complete loss of
power.
! Ensure that the speed of the two communicating Game Boy Color
machines is the same (both double-speed or both normal speed during
communication).
! Noise can be heard from the speaker and headphones during
communication, but this does not indicate a problem with the hardware.
! Be careful that malfunctions/lock-ups do not occur when infrared
communication signals are input from other game software and devices.
Use particular care when using the same subroutine to communicate
between various types of games because malfunctions/lock-ups are
especially likely to occur in such cases. (Before performing data
communication, confirm that the other hardware involved in the
transmission is using the same game. This can be accomplished by
means such as exchanging a unique key code.)
! Though very rare, it is possible that at the final communication stage, one
Game Boy will terminate normally and the other abnormally due to an
unexpected external disturbance.
The following are items to note when using an infrared communication subroutine other
than that provided by Nintendo.
! Ensure that error-handling is implemented to prevent the program from
entering an endless loop when communication is interrupted by sunlight or
obstruction of the signal light.
! To reduce power consumption, use a maximum infrared LED emission
pulse duration of 150 µs and a duty ratio of approximately 1/2.
! Do not leave the infrared LED or photo transistor(Amplifier and Read
Enable) ON when not using infrared communication.
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