NES 2.0 Mapper 419 denotes the Taikee TK-8007 MCU circuit board and compatibles, used by several VT03-based plug 'n play consoles:
The submapper field denotes the same kind of register/opcode scrambling as on NES 2.0 Mapper 256:
| Submapper # | Name | PPU bank affected by ... | CPU bank affected by ... | CPU opcode bytes | ||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| $2012 | $2013 | $2014 | $2015 | $2016 | $2017 | $8000.0 | $8000.1 | $8000.2 | $8000.3 | $8000.4 | $8000.5 | $4107 | $4108 | $8000.6 | $8000.7 | |||
| 0 | Normal | $1000 | $1400 | $1800 | $1C00 | $0000 | $0800 | $0000 | $0800 | $1000 | $1400 | $1800 | $1C00 | $8000 | $A000 | $8000 | $A000 | none |
| 1 | Waixing VT03 | $1400 | $1000 | $0800 | $0000 | $1C00 | $1800 | $1C00 | $1800 | $1400 | $1000 | $0800 | $0000 | $8000 | $A000 | $8000 | $A000 | none |
| 2 | Power Joy Supermax | $1000 | $1400 | $1800 | $1C00 | $0000 | $0800 | $0000 | $0800 | $1000 | $1400 | $1800 | $1C00 | $A000 | $8000 | $A000 | $8000 | none |
| 3 | Zechess/Hummer Team | $0800 | $0000 | $1C00 | $1800 | $1000 | $1400 | $0000 | $0800 | $1000 | $1400 | $1800 | $1C00 | $8000 | $A000 | $8000 | $A000 | none |
| 4 | Sports Game 69-in-1 | $1800 | $0800 | $1000 | $0000 | $1C00 | $1400 | $0000 | $0800 | $1000 | $1400 | $1800 | $1C00 | $8000 | $A000 | $8000 | $A000 | none |
| 5 | Waixing VT02 | $1400 | $1000 | $0800 | $0000 | $0000 | $0800 | $0000 | $0800 | $1000 | $1400 | $1800 | $1C00 | $8000 | $A000 | $8000 | $A000 | none |
| 12 | Cheertone | $1000 | $1400 | $1800 | $1C00 | $0000 | $0800 | $0000 | $0800 | $1000 | $1400 | $1800 | $1C00 | $8000 | $A000 | $8000 | $A000 | D7<->D6, D1<->D2 swapped, switched via $411C |
| 13 | Cube Tech | $1000 | $1400 | $1800 | $1C00 | $0000 | $0800 | $0000 | $0800 | $1000 | $1400 | $1800 | $1C00 | $8000 | $A000 | $8000 | $A000 | D1 and D4 swapped, switched via $4169 |
| 14 | Karaoto | $1000 | $1400 | $1800 | $1C00 | $0000 | $0800 | $0000 | $0800 | $1000 | $1400 | $1800 | $1C00 | $8000 | $A000 | $8000 | $A000 | D6 and D7 swapped, switched via $411C |
| 15 | Jungletac | $1000 | $1400 | $1800 | $1C00 | $0000 | $0800 | $0000 | $0800 | $1000 | $1400 | $1800 | $1C00 | $8000 | $A000 | $8000 | $A000 | D5 and D6 swapped, switched via $4169 |
Instead of normal NES APU audio, the circuit board mounts an ADPCM sound chip that is used for most of the game audio. Command bytes and subsequent data bytes are sent via one of the VT03's general-purpose I/O port in nibblized form:
There is no means of distinguishing a new command byte from its data bytes. Regardless of the current chip state, sending the byte sequence $55 $AA via the above method will reset the chip.
Recognized command bytes:
The procedure for command $06 is as follows:
The input data is composed of frames. One frame is eight bytes/64 bits long and contains the data for 21 output samples, implying three input code bits per sample, decoded bottom-first. If the most significant bit of a 64-bit frame is set, the frame is silent, and all of its lower bits must be ignored.
The decoder maintains two variables of state: a "predictor" (current output) and an "index", both initialized to 0. The lower two bits of the three-bit input code specify one of four 14-element step tables into which the "index" selects a step value, as well as the change of the "index" for the next sample in the form of an index into an index table. The upper bit of the three-bit input code selects the sign of the step value:
indexStep [4] ={ 0, 0, 3, 5 };
indexTable [26] ={ 0, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 20, 20, 20, 20 };
stepTable [4][21] ={
{ 0, 1, 1, 1, 1, 1, 2, 2, 2, 3, 3, 4, 5, 5, 6, 7, 8, 10, 11, 13, 15 },
{ 1, 3, 3, 3, 4, 4, 6, 6, 7, 9, 10, 12, 15, 16, 19, 22, 25, 30, 34, 40, 46 },
{ 3, 5, 5, 6, 7, 8, 10, 11, 13, 16, 18, 21, 25, 28, 32, 38, 43, 51, 58, 68, 78 },
{ 4, 7, 7, 8, 10, 11, 14, 15, 18, 22, 25, 29, 35, 39, 45, 53, 60, 71, 81, 95, 109 }
};
decodeSample (code) {
predictor +=stepTable[code &3][index] *(code &4? -1: 1);
index =indexTable[index +indexStep[code &3]];
}