Chapter 9 Pocket Printer; Chapter 9: Pocket Printer; Overview; Communication Specification - Nintendo GAME BOY Programming Manual

CHAPTER 9: POCKET PRINTER

1. OVERVIEW

These specifications define the serial protocol used to send print and control data from Game Boy to the
Pocket Printer (abbreviated to printer). Game Boy sends data to the printer in packets, and the printer
responds by returning 2 bytes of status information.
2. COMMUNICATION SPECIFICATIONS

2.1 Bidirectional Communication

Serial transfers between Game Boy and the printer are performed in the Game Boy specification
communication format (bidirectional).
The shift clock is furnished by the Game Boy. Both Game Boy and the printer start transmission from
the most significant bit (MSB).
For more information , see Chapter 1, Section 2.5.1, Serial Cable Communication.
7 6

2.2 Transfer Interval For Each Byte

An interval of 270 µs to 5 ms must be interposed between each byte sent. Thus, care should be
exercised regarding factors like interrupts when programming.

2.3 Packets and the Transfer Interval

Each type of data sent by the Game Boy is sent in a packet. An interval of 270 µs to 117 ms must be
allowed between the transfer of each packet. Thus, care should be exercised regarding factors like
interrupts when programming.

2.4 Synchronism Check when Connecting

After the connection between the Game Boy and printer is confirmed, the Game Boy sends a NUL
packet every 100 msec for a synchronism check of the connection. If the Game Boy determines that
a connection is unnecessary and does not send a NUL packet in the prescribed time, the printer will
determine that the connection is abnormal and will wait in an initialized state for a signal from the
Game Boy.
Game Boy
5 4 3 2 1 0
Printer
7 6 5 4 3
237
Chapter 9: Pocket Printer
2 1 0