Difference between revisions of "Default I/O Port Summary"

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|'''Hardware device'''||'''Address'''||'''Read/Write'''||'''b15'''||'''b14'''||'''b13'''||'''b12'''||'''b11'''||'''b10'''||'''b9'''||'''b8'''
 
|'''Hardware device'''||'''Address'''||'''Read/Write'''||'''b15'''||'''b14'''||'''b13'''||'''b12'''||'''b11'''||'''b10'''||'''b9'''||'''b8'''
 
|-
 
|-
−
|Gate Array||&7F||Write Only||0||1||-||-||-||-||-||-
+
|PAL||&7F||Write Only||0||1||-||-||-||-||-||-
 
|-
 
|-
−
|PAL||&7F||Write Only||0||-||-||-||-||-||-||-
+
|Gate Array||&7F||Write Only||0||-||-||-||-||-||-||-
 
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|-
 
|CRTC||&BC-&BF||Read/Write||-||0||-||-||-||-||r1||r0
 
|CRTC||&BC-&BF||Read/Write||-||0||-||-||-||-||r1||r0

Revision as of 03:12, 14 May 2024

This list shows only the internal standard I/O ports, as used in the BIOS ROM of the CPC 464/664/6128 BIOS, and in the AMSDOS ROM of the CPC 664/6128 and DDI-1. For a more complete list, including all Peripherals, see the Complete I/O Port Summary.

I/O Port Mapping

Hardware device Address Read/Write b15 b14 b13 b12 b11 b10 b9 b8
PAL &7F Write Only 0 1 - - - - - -
Gate Array &7F Write Only 0 - - - - - - -
CRTC &BC-&BF Read/Write - 0 - - - - r1 r0
ROM select &DF Write Only - - 0 - - - - -
Printer port &EF Write Only - - - 0 - - - -
8255 PPI &F4-&F7 Read/Write - - - - 0 - r1 r0
Expansion devices &F8-&FB Read/Write - - - - - 0 - -

0 means the bit must be set to 0 for the hardware device to respond, 1 means the bit must be set to 1 for the hardware device to respond, - means this bit is ignored. r1 and r0 mean a bit used to define a register

I/O Ports

I/O Decoded as Port Read Write
#7FXX %01xxxxxx xxxxxxxx Gate Array - Write
#7FXX %0xxxxxxx xxxxxxxx PAL extension to Gate Array for 128K RAM banking - Write
#BCXX %x0xxxx00 xxxxxxxx 6845 CRTC Index - Write
#BDXX %x0xxxx01 xxxxxxxx 6845 CRTC Data Out - Write
#BEXX %x0xxxx10 xxxxxxxx 6845 CRTC Status (as far as supported) Read -
#BFXX %x0xxxx11 xxxxxxxx 6845 CRTC Data In (as far as supported) Read -
#DFXX %xx0xxxxx xxxxxxxx Upper ROM Bank Number - Write
#EFXX %xxx0xxxx xxxxxxxx Printer Port - Write
#F4XX %xxxx0x00 xxxxxxxx 8255 PPI Port A (PSG Data) Read Write
#F5XX %xxxx0x01 xxxxxxxx 8255 PPI Port B (Vsync,PrnBusy,Tape,etc.) Read -
#F6XX %xxxx0x10 xxxxxxxx 8255 PPI Port C (KeybRow,Tape,PSG Control) - Write
#F7XX %xxxx0x11 xxxxxxxx 8255 PPI Control-Register - Write
#F8FF N/A Peripheral Soft Reset (MC_BOOT_PROGRAM and MC_START_PROGRAM do OUT [F8FF],FF) - Write
#FA7E %xxxxx0x0 0xxxxxxx Floppy Motor Control (for 765 FDC) - Write
#FADC %xxxxx0x0 xx0xxx00 Amstrad Serial Interface Z80-SIO / DART port A Data Register Read Write
#FADD %xxxxx0x0 xx0xxx01 Amstrad Serial Interface Z80-SIO / DART port A Control Reg. Read Write
#FADE %xxxxx0x0 xx0xxx10 Amstrad Serial Interface Z80-SIO / DART port B Data Register Read Write
#FADF %xxxxx0x0 xx0xxx11 Amstrad Serial Interface Z80-SIO / DART port B Control Reg. Read Write
#FB7E %xxxxx0x1 0xxxxxx0 765 FDC (internal) Status Register Read -
#FB7F %xxxxx0x1 0xxxxxx1 765 FDC (internal) Data Register Read Write
#FBDC %xxxxx0x1 xx0xxx00 Amstrad Serial Interface 8253 Timer counter 0 Read Write
#FBDD %xxxxx0x1 xx0xxx01 Amstrad Serial Interface 8253 Timer counter 1 Read Write
#FBDE %xxxxx0x1 xx0xxx10 Amstrad Serial Interface 8253 Timer counter 2 Read Write
#FBDF %xxxxx0x1 xx0xxx11 Amstrad Serial Interface 8253 Timer Modus Select - Write
  • The three 765 FDC floppy ports are contained in CPC 664/6128/Plus and DDI-1 only.
  • The eight Amstrad Serial Interface ports are pre-defined as shown above in the AMSDOS ROM. However, neither the CPC 664/6128/Plus nor DDI-1 do actually contain the corresponding RS232 hardware.

Memory Mapped I/O Ports

Mem Decoded as Port Read Write
#4000-7FFF %01xxxxxx xxxxxxxx ASIC - CPC+/GX4000 registers Read Write
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