View source for Mapper

There are three documented memory-mapping chips used on the WonderSwan and Pocket Challenge V2:

* [[Bandai 2001]]
* [[Bandai 2003]]
* [[KARNAK]]

All three provide this same common subset for memory banking:

{| class="wikitable"
! Category
! Port
! Description
! Bits
! Type
! Notes
|-
! rowspan="4" | Extended bankswitching
! $C0
| ROM Linear (EX) Bank
| style="text-align: right" | <tt style="white-space: nowrap">00BB bbbb</tt>
| RW8
| Selects a 1MiB bank accessed via segments 0x4000 through 0xF000.
|-
! $C1
| RAM(/ROM) Bank
| style="text-align: right" | <tt style="white-space: nowrap">bbbb bbbb</tt>
| RW8
| Selects a 64KiB bank accessed via segment 0x1000.
|-
! $C2
| ROM0 Bank
| style="text-align: right" | <tt style="white-space: nowrap">bbbb bbbb</tt>
| RW8
| Selects a 64KiB bank accessed via segment 0x2000.
|-
! $C3
| ROM1 Bank
| style="text-align: right" | <tt style="white-space: nowrap">bbbb bbbb</tt>
| RW8
| Selects a 64KiB bank accessed via segment 0x3000.
|}

Note that the number of bits in the Linear bank register depends on the mapper.

The black-and-white WonderSwan expects that the register at $C3 will power up holding $FF.