SNES Memory Mapping

@Nintendo

Published in 

SNES

 · 4 years ago

 
                      +=-=-=-=-=-=-=-=-=-=-=+ 
                      | SNES Memory Mapping | 
                      |    By: ]SiMKiN[     | 
                      |         v1.0        | 
                      +=-=-=-=-=-=-=-=-=-=-=+ 

 
• LoROM: Mode 20 
• HiROM: Mode 21 

• FastROM's can execute at 3.58Mhz 
• SlowROM's can only execute 2.68Mhz 

  • The SNES lets you access ROM through bank $00 onwards and bank  
    $80 onwards such that locations $00:8000 and $80:8000 are congruent, 
    (they access the same locations.) 
  • When accessing bank $00 onwards the 65816 runs at 2.68Mhz. However,  
    when accessing bank $80 onwards the 65816 can run at 2.68Mhz or  
    3.58Mhz depending on how you set bit 0 of $420D. 

+=========+=============+====================================+=========+ 
| Bank    | Offset      | Definition                         | Shadow  | 
+=========+=============+====================================+=========+ 
| $00-$2f | $0000-$1fff | LowRAM, each bank is shadowed      | $00-$3f | 
|         |             | From bank $7e                      |   $7e   | 
|         | $2000-$2fff | PPU1, APU                          | $00-$3f | 
|         | $3000-$3fff | SFX, DSP, etc.                     | $00-$3f | 
|         | $4000-$41ff | Controller                         | $00-$3f | 
|         | $4200-$5fff | PPU2, DMA, etc.                    | $00-$3f | 
|         | $6000-$7fff | Reserved?                          | $00-$3f | 
|         | $8000-$ffff | (Mode 20, 21 - ROM)                | ------- | 
+---------+-------------+------------------------------------+---------+ 
| $30-$3f | $0000-$1fff | LowRAM, each bank is shadowed      | $00-$3f | 
|         |             | From bank $7e                      |   $7e   | 
|         | $2000-$2fff | PPU1, APU                          | $00-$3f | 
|         | $3000-$3fff | SFX, DSP, etc.                     | $00-$3f | 
|         | $4000-$41ff | Controller                         | $00-$3f | 
|         | $4200-$5fff | PPU2, DMA, etc.                    | $00-$3f | 
|         | $6000-$7fff | (Mode 21 - SRAM) 256KBytes         | ------- | 
|         | $8000-$ffff | (Mode 20, 21 - ROM)                | ------- | 
+---------+-------------+------------------------------------+---------+ 
| $40-$6f | $0000-$7fff | (Mode 21 - ROM)                    | ------- | 
|         | $8000-$ffff | (Mode 20, 21 - ROM)                | ------- | 
+---------+-------------+------------------------------------+---------+ 
| $70-$77 | $0000-$ffff | (Mode 20, 21 - SRAM) 256KBytes     | ------- | 
+---------+-------------+------------------------------------+---------+ 
| $78-$7d | $0000-$ffff | Never Used                         | ------- | 
+---------+-------------+------------------------------------+---------+ 
|   $7e   | $0000-$1fff | LowRAM                             | $00-$3f | 
|         |             | Shadowed to banks $00-$3f          | ------- | 
|         | $2000-$7fff | HighRAM                            | ------- | 
|         | $8000-$ffff | Expanded Ram                       | ------- | 
+---------+-------------+------------------------------------+---------+ 
|   $7f   | $0000-$ffff | More Expanded RAM                  | ------- | 
+---------+-------------+------------------------------------+---------+ 
| $80-$ef | $0000-$ffff | Mirror of $00-$6f                  | $00-$6f | 
+---------+-------------+------------------------------------+---------+ 
| $f0-$ff | $0000-$ffff | (Mode 21 - ROM)                    | ------- | 
+=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-+ 

• ROM: The SNES ROM Image 
• RAM: The SNES Work Memory (WRAM) 
       LowRAM, HighRAM, & Expanded RAM  
       All together = 128 Kilo-Bytes 
• SRAM: Save RAM (Extra RAM added by Cart) 
        The SNES only utilizes 256 Kilo-bits 
        However 256 Kilo-Bytes are provided. 

• APU: Audio Processing Unit 
       SPC700, Inside which has a DSP    
• PPU: Picture Processing Unit 
       PPU1: 5c77-01 
       PPU2: 5c78-03 

• SFX: Super FX Cart Chip, by Nintendo 
• DSP: Digital Signal Processing Cart Chip 
       a.k.a. 'NEC mUPD77C25' 

• Shadow: "Congruent Bank". Same meaning as Mirror. 

          _________________________________________________ 
       .o(_Thanx to: Y0SHi, zsKnight, MrGrim, and MintaBoo_)o.