ROM header: Difference between revisions

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Every WonderSwan ROM contains a header. It is stored at the end - final sixteen bytes - of the ROM image.
The file extensions used to mark WS cartridge files are typically:
 
* <tt>.ws</tt> - "mono" WonderSwan,
* <tt>.wsc</tt> - WonderSwan Color,
* <tt>.pc2</tt> - Pocket Challenge V2.


== ROM header ==
== ROM header ==
Every WonderSwan cartridge ROM contains a header.
The header is stored at the end (the final sixteen bytes) of the ROM image. For this reason, it is also sometimes called a "footer".
A notable consequence of this is that, unlike most other platforms, non-power-of-two ROM images are expected to be padded to the last bank downwards, rather than the first bank upwards; for example, a 768 KiB ROM image will be padded to 1 MiB by appending 256 KiB of padding data to the ''beginning'', rather than the ''end'' of the ROM.


Parts of this header are validated or otherwise used by the console's [[boot ROM]] - they are marked in '''bold'''.
Parts of this header are validated or otherwise used by the console's [[boot ROM]] - they are marked in '''bold'''.
Line 28: Line 38:
| '''$C''' || '''1''' || '''Flags'''
| '''$C''' || '''1''' || '''Flags'''
|-
|-
| $D || 1 || Mapper type
| $D || 1 || Mapper
|-
|-
| $E || 2 || Checksum (sum of all ROM bytes excluding the checksum)
| $E || 2 || Checksum (sum of all ROM bytes excluding the checksum)
|}
|}


=== $5 - Maintenance ===
=== Maintenance ($5) ===
----
----
<pre>
<pre>
Line 47: Line 57:
</pre>
</pre>


=== $6 - Developer/Publisher ID ===
=== Developer/Publisher ID ($6) ===
----
----
{| class="wikitable"
{| class="wikitable"
|+ Known official developer/publisher IDs
|+ Known official developer/publisher IDs
|-
|-
! ID !! Publisher
! ID !! Publisher code !! Publisher
|-
| $01 || BAN || Bandai
|-
|-
| $01 || Bandai
| $02 || TAT || Taito
|-
|-
| $02 || Taito
| $03 || TMY || Tomy
|-
|-
| $03 || ?
| $04 || KEX || Koei
|-
|-
| $04 || Koei
| $05 || DTE || Data East
|-
|-
| $05 || Data East
| $06 || AAE || Asmik Ace
|-
|-
| $06 || Asmik Ace
| $07 || MDE || Media Entertainment
|-
|-
| $07 || Media Entertainment
| $08 || NHB || Nichibutsu
|-
|-
| $08 || Nichibutsu
| $0A || CCJ || Coconuts Japan
|-
|-
| $0A || Coconuts Japan
| $0B || SUM || Sammy
|-
|-
| $0B || Sammy
| $0C || SUN || Sunsoft
|-
|-
| $0C || Sunsoft
| $0D || PAW || Mebius
|-
|-
| $0D || ?
| $0E || BPR || Banpresto
|-
|-
| $0E || Banpresto
| $10 || JLC || Jaleco
|-
|-
| $10 || Jaleco
| $11 || MGA || Imagineer
|-
|-
| $11 || Imagineer
| $12 || KNM || Konami
|-
|-
| $12 || Konami
| $16 || KBS || Kobunsha
|-
|-
| $16 || Kobunsha
| $17 || BTM || Bottom Up
|-
|-
| $17 || Bottom Up
| $18 || KGT || Kaga Tech
|-
|-
| $18 || ?
| $19 || SRV || Sunrise
|-
|-
| $19 || Sunrise
| $1A || CFT || Cyber Front
|-
|-
| $1A || Cyber Front
| $1B || MGH || Megahouse
|-
|-
| $1B || Megahouse
| $1D || BEC || Interbec
|-
|-
| $1D || Interbec
| $1E || NAP || Nihon Application
|-
|-
| $1E || ?
| $1F || BVL || Bandai Visual
|-
|-
| $1F || ?
| $20 || ATN || Athena
|-
|-
| $20 || Athena
| $21 || KDX || KID
|-
|-
| $21 || KID
| $22 || HAL || HAL Corporation
|-
|-
| $22 || ?
| $23 || YKE || Yuki Enterprise
|-
|-
| $23 || ?
| $24 || OMN || Omega Micott
|-
|-
| $24 || Omega Micott
| $25 || LAY || Layup
|-
|-
| $25 || ?
| $26 || KDK || Kadokawa Shoten
|-
|-
| $26 || ?
| $27 || SHL || Shall Luck
|-
|-
| $27 || ?
| $28 || SQR || Squaresoft
|-
|-
| $28 || Squaresoft
| $2A || SCC || ? (SUNCORPORATION?)
|-
|-
| $2A || ?
| $2B || TMC || Tom Create
|-
|-
| $2B || ?
| $2D || NMC || Namco
|-
|-
| $2D || Namco
| $2E || SES || Soeishinsha
|-
|-
| $2E || ?
| $2F || HTR || Hearty Robin
|-
|-
| $2F || ?
| $31 || VGD || Vanguard
|-
|-
| $31 || ?
| $32 || MGT || Megatron
|-
|-
| $32 || ?
| $33 || WIZ || Wiz
|-
|-
| $33 || ?
| $35 || TAN || Tanita
|-
|-
| $36 || ?
| $36 || CPC || Capcom
|}
|}


Note that IDs $00 and $01 are used across a variety of commercial games. Homebrew is known to use arbitrary values in this field.
Note that IDs $00 and $01 are used across a variety of commercial games. Homebrew is known to use arbitrary values in this field.


=== $7 - Color ===
=== Color ($7) ===
----
----
<pre>
<pre>
Line 153: Line 165:
</pre>
</pre>


=== $9 - Game version? / Safe mode ===
=== Game version? / Safe mode ($9) ===
----
----
<pre>
<pre>
Line 168: Line 180:
</pre>
</pre>


=== $A - ROM size ===
=== ROM size ($A) ===
----
----
Unofficial ROM size values are marked in ''italic''.
Unofficial/inferred ROM size values are marked in ''italic''.


{| class="wikitable"
{| class="wikitable"
Line 197: Line 209:
| $09 || 128 Mbit (16 MiB)
| $09 || 128 Mbit (16 MiB)
|-
|-
| ''$0A'' || ''256 Mbit (32 MiB)''<ref name="2003only">Not supported by the [[Bandai 2001]] mapper, which is limited to 16 MiB. The [[Bandai 2003]] mapper is limited to 64 MiB.</ref>
| ''$0A'' || ''256 Mbit (32 MiB)''
|-
|-
| ''$0B'' || ''512 Mbit (64 MiB)''<ref name="2003only"/>
| ''$0B'' || ''512 Mbit (64 MiB)''
|}
|}


=== $B - Save type/size ===
Note that ROM sizes over 16 MiB are not supported by the [[Bandai 2001]] mapper. The [[Bandai 2003]] mapper is limited to 64 MiB.
 
=== Save type/size ($B) ===
----
----
{| class="wikitable"
{| class="wikitable"
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| $00 || colspan="2" style="text-align:center;" | None  
| $00 || colspan="2" style="text-align:center;" | None  
|-
|-
| $01 || rowspan="5" | SRAM || 64 Kbit (8 KiB)
| $01 || rowspan="5" | SRAM || rowspan="2" | 256 Kbit (32 KiB)
|-
|-
| $02 || 256 Kbit (32 KiB)
| $02
|-
|-
| $03 || 1 Mbit (128 KiB)
| $03 || 1 Mbit (128 KiB)
Line 228: Line 242:
|}
|}


=== $C - Flags ===
Note that while ID <code>$01</code> is commonly documented as <code>64 Kbit</code>, all known cartridges using that value come with <code>256 Kbit</code> SRAM chips. This requires further investigation.
 
=== Flags ($C) ===
----
----
<pre>
<pre>
7  bit  0
7  bit  0
---- ----
---- ----
???? ?SBv
???? SB?v
      |||
    || |
      ||+- Starting screen orientation: 0 = Horizontal, 1 = Vertical.
    || +- Starting orientation: 0 = horizontal, 1 = vertical
      ||  Controls the splash screen's orientation.
    |+--- Cartridge ROM width: 0 = 8-bit, 1 = 16-bit
      |+-- ROM bus width: 0 = 16-bit, 1 = 8-bit.
    +---- Cartridge ROM wait state: 0 = +0 cycles, 1 = +1
      +--- ROM access time: 0 = 3 CPU cycles, 1 = 1 CPU cycle.
</pre>
</pre>


=== $D - Mapper type ===
Flag bits 2 and 3 correspond to [[SoC#System Control|System Control]] bits 2 and 3.
 
Bit 0 controls the splash screen's orientation, as well as the LCD segment (horizontal or vertical orientation) displayed during the first 128 ticks of the splash screen.
 
=== Mapper ($D) ===
----
----
{| class="wikitable"
{| class="wikitable"
Line 248: Line 267:
! ID !! Mapper
! ID !! Mapper
|-
|-
| $00 || [[Bandai 2001]]
| $00 || [[Bandai 2001]] or [[KARNAK]]
|-
|-
| $01 || [[Bandai 2003]]
| $01 || [[Bandai 2003]]
|-
| $02 || [[KARNAK]] (Pocket Challenge V2)
|}
|}

Revision as of 18:52, 23 April 2025

The file extensions used to mark WS cartridge files are typically:

  • .ws - "mono" WonderSwan,
  • .wsc - WonderSwan Color,
  • .pc2 - Pocket Challenge V2.

ROM header

Every WonderSwan cartridge ROM contains a header.

The header is stored at the end (the final sixteen bytes) of the ROM image. For this reason, it is also sometimes called a "footer".

A notable consequence of this is that, unlike most other platforms, non-power-of-two ROM images are expected to be padded to the last bank downwards, rather than the first bank upwards; for example, a 768 KiB ROM image will be padded to 1 MiB by appending 256 KiB of padding data to the beginning, rather than the end of the ROM.

Parts of this header are validated or otherwise used by the console's boot ROM - they are marked in bold.

Header contents
Offset Length Contents
$0 5 Far jump instruction: 0xEA, offset, segment.
$5 1 Maintenance
$6 1 Developer/Publisher ID
$7 1 Color
$8 1 Game ID (binary-coded decimal)
$9 1 Game version? / Safe mode
$A 1 ROM size
$B 1 Save type/size
$C 1 Flags
$D 1 Mapper
$E 2 Checksum (sum of all ROM bytes excluding the checksum)

Maintenance ($5)

7  bit  0
---- ----
s... 0000
|    ||||
|    ++++- Must be zero; otherwise the console will prohibit execution.
|          Purpose unknown.
+--------- (Color) Splash bypass: 0 = Disable, 1 = Enable.
           Bypasses the custom boot splash stored in the console's
           internal EEPROM; presumably used for bricked console recovery.

Developer/Publisher ID ($6)

Known official developer/publisher IDs
ID Publisher code Publisher
$01 BAN Bandai
$02 TAT Taito
$03 TMY Tomy
$04 KEX Koei
$05 DTE Data East
$06 AAE Asmik Ace
$07 MDE Media Entertainment
$08 NHB Nichibutsu
$0A CCJ Coconuts Japan
$0B SUM Sammy
$0C SUN Sunsoft
$0D PAW Mebius
$0E BPR Banpresto
$10 JLC Jaleco
$11 MGA Imagineer
$12 KNM Konami
$16 KBS Kobunsha
$17 BTM Bottom Up
$18 KGT Kaga Tech
$19 SRV Sunrise
$1A CFT Cyber Front
$1B MGH Megahouse
$1D BEC Interbec
$1E NAP Nihon Application
$1F BVL Bandai Visual
$20 ATN Athena
$21 KDX KID
$22 HAL HAL Corporation
$23 YKE Yuki Enterprise
$24 OMN Omega Micott
$25 LAY Layup
$26 KDK Kadokawa Shoten
$27 SHL Shall Luck
$28 SQR Squaresoft
$2A SCC ? (SUNCORPORATION?)
$2B TMC Tom Create
$2D NMC Namco
$2E SES Soeishinsha
$2F HTR Hearty Robin
$31 VGD Vanguard
$32 MGT Megatron
$33 WIZ Wiz
$35 TAN Tanita
$36 CPC Capcom

Note that IDs $00 and $01 are used across a variety of commercial games. Homebrew is known to use arbitrary values in this field.

Color ($7)

7  bit  0
---- ----
???? ???c
        |
        +- 0 = Monochrome only, 1 = Supports Color mode.

Game version? / Safe mode ($9)

7  bit  0
---- ----
pvvv vvvv
|||| ||||
|+++ ++++- Game version?
+--------- Internal EEPROM write protect: 0 = Enable, 1 = Disable.
           This prohibits writing to the internal EEPROM for addresses
           0x60 and above (user settings, custom splash screen).
           Games are expected to enable write protection; however, the
           WonderWitch is factory configured with it disabled.

ROM size ($A)

Unofficial/inferred ROM size values are marked in italic.

ROM size values
ID Size
$00 1 Mbit (128 KiB)
$01 2 Mbit (256 KiB)
$02 4 Mbit (512 KiB)
$03 8 Mbit (1 MiB)
$04 16 Mbit (2 MiB)
$05 24 Mbit (3 MiB)
$06 32 Mbit (4 MiB)
$07 48 Mbit (6 MiB)
$08 64 Mbit (8 MiB)
$09 128 Mbit (16 MiB)
$0A 256 Mbit (32 MiB)
$0B 512 Mbit (64 MiB)

Note that ROM sizes over 16 MiB are not supported by the Bandai 2001 mapper. The Bandai 2003 mapper is limited to 64 MiB.

Save type/size ($B)

Save type values
ID Type Size
$00 None
$01 SRAM 256 Kbit (32 KiB)
$02
$03 1 Mbit (128 KiB)
$04 2 Mbit (256 KiB)
$05 4 Mbit (512 KiB)
$10 EEPROM 1 Kbit (128 B)
$20 16 Kbit (2 KiB)
$50 8 Kbit (1 KiB)

Note that while ID $01 is commonly documented as 64 Kbit, all known cartridges using that value come with 256 Kbit SRAM chips. This requires further investigation.

Flags ($C)

7  bit  0
---- ----
???? SB?v
     || |
     || +- Starting orientation: 0 = horizontal, 1 = vertical
     |+--- Cartridge ROM width: 0 = 8-bit, 1 = 16-bit
     +---- Cartridge ROM wait state: 0 = +0 cycles, 1 = +1

Flag bits 2 and 3 correspond to System Control bits 2 and 3.

Bit 0 controls the splash screen's orientation, as well as the LCD segment (horizontal or vertical orientation) displayed during the first 128 ticks of the splash screen.

Mapper ($D)

Known mapper types
ID Mapper
$00 Bandai 2001 or KARNAK
$01 Bandai 2003
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