Does it deal with gecko registers or the actual registers? The codetype document uses rN & rM instead of grN & grM but the Wii has 31 registers and the value of a single character in hex only goes up to 15
Those are gecko registers.
You have to use ASM codes if you want to acces the actual registers.
What he said.. Gecko registers are mostly used for typical add x to something codes.
An example would be (no actual codes but each of the following lines can translate into one single code line):
If button a is pressed
Read value of address XXXXXXXX to gr0
Add 200 to gr0
Write value of g0 to address XXXXXXXX
Terminator