SH2 Assembly programming for the 32x

The 32x was an upgrade to the Genesis. Plugging onto the Genesis, and overlaying it's video via connecting video cables. it's a rather odd, but 'somewhat' effective solution to upgrading the Genesis.  Unfortunately consumer confusion (and the upcoming saturn) left the 32x dead in the water, and it was a commercial failure.

While graphically capable, and with some sound functions, it also uses the Genesis for it's music chip, and joypad access (VIA a separate 68000 program)... many games also used the Genesis VDP for some graphics!

In fact, execution starts on the 68000 side, so it is impossible to have a SH2 only 32x cartridge.





Cpu Dual SH2 (23mhz)
Ram 256K Ram
Video 256k Vram
Resolution 320x240
Sound PCM + Genesis sound


Genesis 68000 Memory Map

The 32x add on changes the Genesis memory map:

Address   
Purprose
$000000 Vector Rom
$400000 Same as Megadrive
$840000 Frame buffer
$860000 Overwrite Image
$880000 Rom Cartridge
$900000 Rom Cartridge (4 bank swtch)
$A00000 Same as Megadrive
$A130EC Super32x ID
$A130F0 Same as Megadrive
$A15100 Super32x Sys Reg
$A15180 VDP Regs
$A15200 Color Palette
$A15400 Same as Megadrive

Genesis 68000 Hardware Registers

Address  
Purpose Bits                            
Details
$A5100 Adapter Control Register %F-------R-----rA F=VDP Access Auth (1=sh2 0=md) R=Sh2 Reset enable r=reset(0=reset) A=Adapter enable (1=32x on)
$A5102 Interrupt control register %--------------SM S=Slave sh2 interrupt M=Master SH2 interrupt
$A5104 Bank Set Register %--------------BB Bank in $900000-$9FFFFF
$A5106 DREQ control register %--------F----S0R F=1=Full R=1=rom to vram start
$A5108 DREQ Source Reg H %--------HHHHHHHH
$A510A DREQ Source Reg L %LLLLLLLLLLLLLLL0
$A510C DREQ Dest Reg H %--------HHHHHHHH
$A510E DREQ Dest Reg L %LLLLLLLLLLLLLLL0
$A5110 DREQ Length %LLLLLLLLLLLLLL00 No of words to transfer
$A5112 FIFO Reg %????????????????
$A511A Sega TV Register %---------------C C=0=Rom 1=Dram
$A5120 2way Coms with SH2
($20004020 on SH2)
$A5122 2way Coms with SH2
($20004022 on SH2)
$A5124 2way Coms with SH2
($20004024 on SH2)
$A5126 2way Coms with SH2
($20004026 on SH2)
$A5128 2way Coms with SH2
($20004028 on SH2)
$A512A 2way Coms with SH2
($2000402A on SH2)
$A512C 2way Coms with SH2
($2000402C on SH2)
$A512E 2way Coms with SH2
($2000402E on SH2)
$A5130 PWM Sound Source Control Reg %----TTTTR---rrLL T=Timer interrupt interval R=Dreq1 occurrence enable lr=L/R
$A5132 Cycle Register %----CCCCCCCCCCCC Cycle counter
$A5134 L ch pulse width %FE--DDDDDDDDDDDD FE=Full/Empty (read) D=Data (Write)
$A5136 R ch pulse width %FE--DDDDDDDDDDDD FE=Full/Empty (read) D=Data (Write)
$A5138 mono pulse width %FE--DDDDDDDDDDDD FE=Full/Empty (read) D=Data (Write)
$A5180 Bitmap Mode Register %P-------pL----MM


32X SH2 Memory Map

Here is the Memory map as seen by the SH2

Cache Through Address 
Cache Address 
Purpose
$20000000 $00000000 Boot Rom
$20004000 $00004000 Super 32x Sys Reg
$20004100 $00004100 VDP Reg
$20004200 $00004200 Color Palette
$20004400 $00004400 -
$22000000 $02000000 Rom Cartridge
$22400000 $02400000 -
$24000000 $04000000 Frame Buffer (Vram)
$24020000 $04020000 Overwrite Image
$24040000 $04040000 -
$26000000 $06000000 SDRAM
$26040000 $06040000 -
$28000000 $08000000


32X SH2
Hardware Registers


68000 Equivalent SH2 Cache Through Address Purpose Bits Details

$20040000 Interrupt mask %F-----ACH---VHCP F=Vdp access (0=MD 1=SH2) A=Adapter enable (1=32x on) C=Cart in?(1=no) H=H-int(1=on) C=Command int on P=PWM timer interrupt

$20040002 Stand by change register Used by System Boot Rom only

$20040004 Hcount Register %--------HHHHHHHH H=Hint occurrence
$A5106 $20040006 DREQ Control register %FE-----------S0R F=1=Full E=1=Empty
$A5108 $20040008 DREQ Source Reg H %--------HHHHHHHH
$A510A $2004000A DREQ Source Reg L %LLLLLLLLLLLLLLL0
$A510C $2004000C DREQ Dest Reg H %--------HHHHHHHH
$A510E $2004000E DREQ Dest Reg L %LLLLLLLLLLLLLLL0
$A5110 $20040010 DREQ Length %LLLLLLLLLLLLLL00 No of words to transfer
$A5112 $20040012 FIFO Reg %????????????????

$20004014 Vres interrupt clear


$20004016 V interrupt clear


$20004018 H interrupt clear


$2000401A Cmd interrupt clear


$2000401C Pwm interrupt clear

$A5120 $20040020 2way Coms with SH2 ($A5120 on 68000)
$A5122 $20040022 2way Coms with SH2 ($A5122 on 68000)
$A5124 $20040024 2way Coms with SH2 ($A5124 on 68000)
$A5126 $20040026 2way Coms with SH2 ($A5126 on 68000)
$A5128 $20040028 2way Coms with SH2 ($A5128 on 68000)
$A512A $2004002A 2way Coms with SH2 ($A512A on 68000)
$A512C $2004002C 2way Coms with SH2 ($A512C on 68000)
$A512E $2004002E 2way Coms with SH2 ($A512E on 68000)
$A5130 $20040030 PWM Sound Source Control Reg %----TTTTR---rrLL T=Timer interrupt interval R=Dreq1 occurrence enable lr=L/R
$A5132 $20040032 Cycle Register %----CCCCCCCCCCCC Cycle counter
$A5134 $20040034 L ch pulse width %FE�DDDDDDDDDDDD FE=Full/Empty (read) D=Data (Write)
$A5136 $20040036 R ch pulse width %FE�DDDDDDDDDDDD FE=Full/Empty (read) D=Data (Write)
$A5138 $20040038 mono pulse width %FE�DDDDDDDDDDDD FE=Full/Empty (read) D=Data (Write)
$A5180 $20040100 Bitmap Mode Register %P-------pL----MM P=Pal/Ntcs p+priority(1=32x) L=240 line? M=screen mode (pixel format)
$A5182 $20040102 Screen Shift Control %---------------S S=Shift 1 dot
$A5184 $20040104 Auto Fill Length ^--------LLLLLLLL Length to fill in words
$A5186 $20040106 Auto Fill Start Address %AAAAAAAAAAAAAAAA A=Address
$A518A $2004010D Auto Fill Data %DDDDDDDDDDDDDDDD D=Data to fill
$A518A $2004010A Frame Buffer control reg %VHP-----------FS V=Vblank H=Hblank P=Palette accessable F=frame buffer accessible S=Swap vram to VDP






 

View Options
Default Dark
Simple (Hide this menu)
Print Mode (white background)

Top Menu
***Main Menu***
Youtube channel
Patreon
Introduction to Assembly (Basics for absolute beginners)
Amazon Affiliate Link
AkuSprite Editor
ChibiTracker
Dec/Bin/Hex/Oct/Ascii Table

Alt Tech
Archive.org
Bitchute
Odysee
Rumble
DailyMotion
Please note: I wlll upload more content to these alt platforms based on the views they bring in

Z80 Content
***Z80 Tutorial List***
Learn Z80 Assembly (2021)
Learn Z80 Assembly (old)
Hello World
Simple Samples
Advanced Series
Multiplatform Series
Platform Specific Series
ChibiAkumas Series
Grime Z80
Z80 Downloads
Z80 Cheatsheet
Sources.7z
DevTools kit
Z80 Platforms
Amstrad CPC
Elan Enterprise
Gameboy & Gameboy Color
Master System & GameGear
MSX & MSX2
Sam Coupe
TI-83
ZX Spectrum
Spectrum NEXT
Camputers Lynx

6502 Content
***6502 Tutorial List***
Learn 6502 Assembly
Advanced Series
Platform Specific Series
Hello World Series
Simple Samples
Grime 6502
6502 Downloads
6502 Cheatsheet
Sources.7z
DevTools kit
6502 Platforms
Apple IIe
Atari 800 and 5200
Atari Lynx
BBC Micro
Commodore 64
Commodore PET
Commander x16
Super Nintendo (SNES)
Nintendo NES / Famicom
PC Engine (Turbografx-16)
Vic 20

68000 Content
***68000 Tutorial List***
Learn 68000 Assembly
Hello World Series
Platform Specific Series
Simple Samples
Grime 68000
68000 Downloads
68000 Cheatsheet
Sources.7z
DevTools kit
68000 Platforms
Amiga 500
Atari ST
Neo Geo
Sega Genesis / Mega Drive
Sinclair QL
X68000 (Sharp x68k)

8086 Content
Learn 8086 Assembly
Platform Specific Series
Hello World Series
Simple Samples
8086 Downloads
8086 Cheatsheet
Sources.7z
DevTools kit
8086 Platforms
Wonderswan
MsDos

ARM Content
Learn ARM Assembly
Learn ARM Thumb Assembly
Platform Specific Series
Hello World
Simple Samples
ARM Downloads
ARM Cheatsheet
Sources.7z
DevTools kit
ARM Platforms
Gameboy Advance
Nintendo DS
Risc Os

Risc-V Content
Learn Risc-V Assembly
Risc-V Downloads
Risc-V Cheatsheet
Sources.7z
DevTools kit

MIPS Content
Learn Risc-V Assembly
Platform Specific Series
Hello World
Simple Samples
MIPS Downloads
MIPS Cheatsheet
Sources.7z
DevTools kit
MIPS Platforms
Playstation
N64

PDP-11 Content
Learn PDP-11 Assembly
Platform Specific Series
Simple Samples
PDP-11 Downloads
PDP-11 Cheatsheet
Sources.7z
DevTools kit
PDP-11 Platforms
PDP-11
UKNC

TMS9900 Content
Learn TMS9900 Assembly
Platform Specific Series
Hello World
TMS9900 Downloads
TMS9900 Cheatsheet
Sources.7z
DevTools kit
TMS9900 Platforms
Ti 99

6809 Content
Learn 6809 Assembly
Learn 6309 Assembly
Platform Specific Series
Hello World Series
Simple Samples
6809 Downloads
6809/6309 Cheatsheet
Sources.7z
DevTools kit
6809 Platforms
Dragon 32/Tandy Coco
Fujitsu FM7
TRS-80 Coco 3
Vectrex

65816 Content
Learn 65816 Assembly
Hello World
Simple Samples
65816 Downloads
65816 Cheatsheet
Sources.7z
DevTools kit
65816 Platforms
SNES

eZ80 Content
Learn eZ80 Assembly
Platform Specific Series
eZ80 Downloads
eZ80 Cheatsheet
Sources.7z
DevTools kit
eZ80 Platforms
Ti84 PCE

IBM370 Content
Learn IBM370 Assembly
Simple Samples
IBM370 Downloads
IBM370 Cheatsheet
Sources.7z
DevTools kit

Super-H Content
Learn SH2 Assembly
Hello World Series
Simple Samples
SH2 Downloads
SH2 Cheatsheet
Sources.7z
DevTools kit
SH2 Platforms
32x
Saturn

PowerPC Content
Learn PowerPC Assembly
Hello World Series
Simple Samples
PowerPC Downloads
PowerPC Cheatsheet
Sources.7z
DevTools kit
PowerPC Platforms
Gamecube

Work in Progress
ChibiAndroids

Misc bits
Ruby programming









Buy my Assembly programming book
on Amazon in Print or Kindle!


Buy my Assembly programming book





Available worldwide!
Search 'ChibiAkumas' on
your local Amazon website!
Click here for more info!



































































































Buy my Assembly programming book
on Amazon in Print or Kindle!


Buy my Assembly programming book





Available worldwide!
Search 'ChibiAkumas' on
your local Amazon website!
Click here for more info!


























































































Buy my Assembly programming book
on Amazon in Print or Kindle!


Buy my Assembly programming book





Available worldwide!
Search 'ChibiAkumas' on
your local Amazon website!
Click here for more info!