View source for Bandai 2003

In addition to the normal [[Mapper]] banking interface, Bandai's 2003 adds registers for an RTC interface, GPO pins, self flashing, and accessing more than 16MiB of ROM.

{| class="wikitable"
! Category
! Port
! Description
! Bits
! Type
! Notes
|-
! rowspan="3" | RTC
! rowspan="2" | $CA
| RTC Command
| style="text-align: right" | <tt style="white-space: nowrap">...1 CCCC</tt>
| W8
| Command (C)
|-
| RTC Status
| style="text-align: right" | <tt style="white-space: nowrap">D00B CCCC</tt>
| R8
| Busy (B), Command (C), Data needed (D)
|-
! $CB
| RTC Payload
| style="text-align: right" | <tt style="white-space: nowrap">dddd dddd</tt>
| RW8
| Data (d)
|-
! rowspan="2" | GPO
! $CC
| GPO Data Direction
| style="text-align: right" | <tt style="white-space: nowrap">0000 oooo</tt>
| RW8
| 1 = output, 0 = high-impedance (weak pull-down)
|-
! $CD
| GPO Data
| style="text-align: right" | <tt style="white-space: nowrap">0000 dddd</tt>
| RW8
| 1 = 3V, if enabled by data direction
|-
! Self-Flash
! $CE
| Self-Flash Control
| style="text-align: right" | <tt style="white-space: nowrap">0000 000r</tt>
| RW8
| 1 = ROM is accessible at segment 0x1000;
0 = RAM instead.
|-
! rowspan="4" | Extended bankswitching
! $CF
| 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. Identical to the register at 0xC0.
|-
! $D0
| RAM(/ROM) Bank
| style="text-align: right" | <tt style="white-space: nowrap">0000 00bb bbbb bbbb</tt>
| RW16
| Selects a 64KiB bank accessed via segment 0x1000. Lower 8 bits are identical to the register at 0xC1.
|-
! $D2
| ROM0 Bank
| style="text-align: right" | <tt style="white-space: nowrap">0000 00bb bbbb bbbb</tt>
| RW16
| Selects a 64KiB bank accessed via segment 0x2000. Lower 8 bits are identical to the register at 0xC2.
|-
! $D4
| ROM1 Bank
| style="text-align: right" | <tt style="white-space: nowrap">0000 00bb bbbb bbbb</tt>
| RW16
| Selects a 64KiB bank accessed via segment 0x3000. Lower 8 bits are identical to the register at 0xC3.
|}

Not all PCBs are wired to support self-flashing. Not all ROMs have the needed /BYTE pin. Even on PCBs without support, ROM can still be enabled by writing to port $CE.

== 2003 RTC interface ==
The 2003's RTC interface is a simple half-duplex SPI-like protocol. A write to $CA will start a transaction, depending on the exact value written.

If there is no external S-3511A, all bytes will read back as $FF due to a weak pull-up inside the 2003.

For specifics of what the S-3511A expects to be done with these bytes, see [[Real-Time Clock]].

(Put logic analyzer traces here)

Values are as follows:

=== $00-$0F, $1C-$1F ===
Immediately stop the transaction. This cannot be safely used to abort an ongoing transaction, because the 2003 still relays the 384kHz clock. In contrast, normal termination stops relaying that clock.

=== $10, $11 ===
Send command byte ($60 or $61 respectively) and stop.

=== $12 ===
Send command byte ($62), then send byte stored in $CB, then stop. The 2003 expects that the value in $CB is valid and does not pause if the CPU hasn't yet written a value.

=== $13 ===
Send command byte ($63), then receive byte, then stop. After the "data needed" is set or the "busy" bit is clear the value can be read from $CB.

=== $14 ===
Send command byte ($64), then send seven bytes of payload, then stop. The 2003 expects that the ''first'' byte is preloaded in $CB, but pauses for the CPU to write each subsequent byte by setting the "Data needed" bit.

=== $15 ===
Send command byte ($65), then receive seven bytes of payload, then stop. The 2003 pauses for the CPU to read each subsequent byte by setting the "Data needed" bit.

=== $16 ===
Send command byte ($66), then send three bytes of payload, then stop.

=== $17 ===
Send command byte ($67), then receive three bytes of payload, then stop.

=== $18, $1A ===
Send command byte ($68 or $6A), then send two bytes of payload, then stop.

=== $19, $1B ===
Send command byte ($69 or $6B), then receive two bytes of payload, then stop.