V810

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The RISC CPU used in the PC-FX clocked at 21.477MHz.

The V810 CPU memory bus in the PC-FX runs in 16-bit mode(versus 32-bit mode).

CPU Memory Map

Memory range R/W Description
$00000000 - $001FFFFF R/W 1MB Internal RAM
$80000000 - $80000FFF? R?/W? Possibly a mirror of the I/O port map.
$80700000 - $807FFFFF R "EXTIO" boot ROM.
$A0000000 - $A3FFFFFF R HuC6261 (VCE) Palette RAM Data Port Read, intended for use with bitstring instructions.
$A4000000 - $A7FFFFFF R HuC6270 (VDC-A) VRAM Data Port Read, intended for use with bitstring instructions.
$A8000000 - $ABFFFFFF R HuC6270 (VDC-B) VRAM Data Port Read, intended for use with bitstring instructions.
$AC000000 - $AFFFFFFF R HuC6272 (KING) KRAM Data Port Read, intended for use with bitstring instructions.
$B0000000 - $B3FFFFFF W HuC6261 Palette RAM Data Port Write, intended for use with bitstring instructions.
$B4000000 - $B7FFFFFF W HuC6270 (VDC-A) VRAM Data Port Write, intended for use with bitstring instructions.
$B8000000 - $BBFFFFFF W HuC6270 (VDC-B) VRAM Data Port Write, intended for use with bitstring instructions.
$BC000000 - $BFFFFFFF W HuC6272 (KING) KRAM Data Port Write, intended for use with bitstring instructions.
$E0000000 - $E7FFFFFF R/W 32KB Internal Backup RAM. Not present on the PC-FXGA. It is apparently 8-bit RAM, so the upper byte on 16-bit writes is ignored, and the address into the RAM is calculated like: (Address >> 1) & 0x7FFF
$E8000000 - $EFFFFFFF R/W External Backup RAM
$FFF00000 - $FFFFFFFF R 2MB BIOS ROM


CPU I/O Port Map

Port range R/W Description
$00000000 - $000000FF R/W Keyport.
$00000100 - $000001FF W HuC6230 (SoundBox)
$00000200 - $000002FF W HuC6271 (RAINBOW)
$00000300 - $000003FF R/W HuC6261 (VCE)
$00000400 - $000004FF R/W HuC6270 (VDC-A)
$00000500 - $000005FF R/W HuC6270 (VDC-B)
$00000600 - $000006FF R/W HuC6272 (KING)
$00000700 - $0000071F W Expansion bus reset register(D0 = 1, reset? level sensitive?)
$00000C00 - $00000C3F R HuC6270 (VDC-A) "address keep register"
$00000C40 - $00000C7F R HuC6270 (VDC-B) "address keep register"
$00000C80 - $00000CBF R/W Backup Memory Control
$00000CC0 - $00000CFF R "Gatearray version register"
$00000E00 - $00000EFF R/W IRQ Control
$00000F00 - $00000FFF R/W Timer Control
$80500000 - $80510000 R/W HuC6273 (3D)


Official Documentation

V810 Family Architecture