參考資料：
http://nesdev.com/6502.txt
http://wiki.nesdev.com/w/index.php/Nesdev_Wiki
http://www.6502.org/tutorials/6502opcodes.html
https://www.masswerk.at/6502/6502_instruction_set.html
| 8 Bits | 8 Bits | Description |
|---|---|---|
| A | Accumulator | |
| X | X Rrgister | |
| Y | Y Register | |
| SP | Stack Pointer | |
| SR | Status Register | |
| PC | Program Counter | |
| $2000 | PPUCTRL | |
| $2001 | PPUMASK | |
| $2002 | PPUSTATUS | |
| $2003 | OAMADDR | |
| $2004 | OAMDATA | |
| $2005 | PPUSCROLL | |
| $2006 | PPUADDR | |
| $2007 | PPUDATA | |
| $4000 | SQ1_VOL, Duty and volume for square wave 1 | |
| $4001 | SQ1_SWEEP, Sweep control register for square wave 1 | |
| $4002 | SQ1_LO, Low byte of period for square wave 1 | |
| $4003 | SQ1_HI, High byte of period and length counter value for square wave 1 | |
| $4004 | SQ2_VOL, Duty and volume for square wave 2 | |
| $4005 | SQ2_SWEEP, Sweep control register for square wave 2 | |
| $4006 | SQ2_LO, Low byte of period for square wave 2 | |
| $4007 | SQ2_HI, High byte of period and length counter value for square wave 2 | |
| $4008 | TRI_LINEAR, Triangle wave linear counter | |
| $4009 | Unused, but is eventually accessed in memory-clearing loops | |
| $400A | TRI_LO, Low byte of period for triangle wave | |
| $400B | TRI_HI, High byte of period and length counter value for triangle wave | |
| $400C | NOISE_VOL, Volume for noise generator | |
| $400D | Unused, but is eventually accessed in memory-clearing loops | |
| $400E | NOISE_LO, Period and waveform shape for noise generator | |
| $400F | NOISE_HI, Length counter value for noise generator | |
| $4010 | DMC_FREQ, Play mode and frequency for DMC samples | |
| $4011 | DMC_RAW, 7-bit DAC | |
| $4012 | DMC_START, Start of DMC waveform is at address $C000 + $40*$xx | |
| $4013 | DMC_LEN, Length of DMC waveform is $10*$xx + 1 bytes (128*$xx + 8 samples) | |
| $4014 | OAMDMA, Writing $xx copies 256 bytes by reading from $xx00-$xxFF and writing to OAMDATA ($2004) | |
| $4015 | SND_CHN, Sound channels enable and status | |
| $4016 | JOY1, Joystick 1 data (R) and joystick strobe (W) | |
| $4017 | JOY2, Joystick 2 data (R) and frame counter control (W) | |
| $4018-$401F | APU and I/O functionality that is normally disabled. See CPU Test Mode. | |
Status
| Bit7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
|---|---|---|---|---|---|---|---|
| (S) Sign flag | (V) Overflow flag | (B) Software interrupt flag | (D) BCD | (I)Interrupt enable/disable flag | (Z) Zero flag | (C) Carry flag |