Nintendo GAME BOY Programming Manual page 171

Note: If all addresses from 04h to 06h are set to 0, the NMI jumps to the
original vector. NMI is disabled in the system program, so it must be
enabled to be used.
Command: CHR_TRN (Code: 13h)
(Data Transfer using VRAM) Function: Transfers Super NES character format data.
d7
1 0 0
00h
01h -- --
Note: The 4 Kbytes of SGB RAM data immediately following this command is
handled as Super NES character data and transferred to Super NES
VRAM.
The format of the tranferred data is based on the Super NES character
data format.
The BG character names are allocated to 00h – FFh.
When character data is used for the picture frame, characters with a
character name setting of 0x00 should consist of null bits, and all dots
of characters with a name setting of 0x01 should be represented by non-
null bits.
Command: PCT_TRN (Code: 14h)
(Data Transfer using VRAM)
Function: Transfers screen data and color data for picture frames created by the software
developer.
d0
1 1 0 0 1
-- -- -- -- 0
Chapter 6: The Super Game Boy System
Number of packets: 1h (fixed)
Command code: 13h
0: Data for characters 00h – 7Fh
(BG)
1: Data for characters 80h – FFh
(BG)
The characters are in 16-color (4-bit) mode.
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