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Name Description Type Polarity Comes from Fault consequence
24M 24MHz master clock Clock NEO-D0 Nothing works
12M 12MHz clock (24/2) non-inverted Clock NEO-D0 Bad graphics
  • 8M: 8MHz clock (24/3) non-inverted from LSPC
  • 6MB: 6MHz clock (24/4) inverted from NEO-D0
  • 4M: 4MHz clock (24/6) non-inverted from LSPC
  • 4MB: 4MHz clock (24/6) inverted from LSPC+AS04
  • 1MB: 3MHz clock (24/8) inverted from NEO-D0
  • 68KCLK: 12MHz clock (24/2) non-inverted from NEO-D0 (always equivalent to 12M ?)
  • 68KCLKB: 12MHz clock (24/2) inverted from NEO-D0
  • 2H1: S ROM A3
  • A1~A23: 68k address bus
  • A22I,A23I: A22 and A23 modified for 68k vector table swap
  • AS: 68k Address Strobe
  • BNK0~2: Memory card bank selection
  • CA4: C ROMs A4
  • C* or CR0~CR31: C ROMs data bus (2*16bits), holds data for one 8-pixels line
  • D0~D15: 68k data bus
  • /DTACK: 68k Data Transmit ACKnowledge, used to slow down acces to memory (see wait cycles)
  • FIXD0~FIXD7: Fix layer data bus, holds data for 2 pixels
  • P0~P23: C ROM, S ROM, LO ROM and internal address/data bus (multiplexed P bus)
  • PA0~PA11: Palette RAM address bus
  • PAL: Palette RAM address decode for 68k access
  • PCK1B: Low 55ns, high 610 (1.5MHz) Clock to latch C ROM address from P0~P23 (mapping) on rising edge.
  • PCK2B: Low 55ns, high 610 (1.5MHz) Clock to latch S ROM address from P0~P15 (mapping) on rising edge.
  • /PORTADRS: $200000-$2FFFFF (P2+ ROM/Security chip) any access
  • /PORTOEL: $200000-$2FFFFF (P2+ ROM/Security chip) odd byte read
  • /PORTOEU: $200000-$2FFFFF (P2+ ROM/Security chip) even byte read
  • /PORTWEL: $200000-$2FFFFF (P2+ ROM/Security chip) odd byte write
  • /PORTWEU: $200000-$2FFFFF (P2+ ROM/Security chip) even byte write
  • /PWAIT0, /PWAIT1: adds 0 to 3 cycle delay for P2 ROM reads, see wait cycles
  • R/W: 68k Read/Write
  • /ROMOE: $000000-$0FFFFF (P1 ROM) read
  • /ROMOEL: $000000-$0FFFFF (P1 ROM) odd byte read
  • /ROMOEU: $000000-$0FFFFF (P1 ROM) even byte read
  • /ROMWAIT: add 1-cycle delay for P1 ROM reads
  • /SROMOE: $C00000-$CFFFFF (System ROM) read
  • /SROMOEL: $C00000-$CFFFFF (System ROM) odd byte read
  • /SROMOEU: $C00000-$CFFFFF (System ROM) even byte read
  • SDA0~SDA15 : Z80 address bus
  • SDD0~SDD7: Z80 data bus
  • SDRAD0~SDRAD7: ADPCM-A ROM multiplexed bus (data/address)
  • SDRA8,SDRA9,SDRA20~SDRA23: ADPCM-A ROM address bus
  • SDPAD0~SDPAD7: ADPCM-B ROM multiplexed bus (data/address)
  • SDPA8,SDPA9,SDPA10,SDPA11: ADPCM-B ROM address bus
  • SYSTEM: low when onboard ROMs selected
  • SYSTEMB: inverted SYSTEM