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

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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 [[I/O Port Summary|Complete I/O Port Summary]].
 
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 [[I/O Port Summary|Complete I/O Port Summary]].
  
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== I/O Port Mapping ==
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<br>
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{|{{Prettytable|width: 700px; font-size: 2em;}}
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|'''Hardware device'''||'''Address'''||'''Read/Write'''||'''b15'''||'''b14'''||'''b13'''||'''b12'''||'''b11'''||'''b10'''||'''b9'''||'''b8'''
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|Gate Array||&7F||Write Only||0||1||-||-||-||-||-||-
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|PAL||&7F||Write Only||0||(1)||-||-||-||-||-||-
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|CRTC Select||&BC||Write Only||-||0||-||-||-||-||0||0
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|CRTC Write||&BD||Write Only||-||0||-||-||-||-||0||1
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|CRTC Status||&BE||Read Only||-||0||-||-||-||-||1||0
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|CRTC Read||&BF||Read Only||-||0||-||-||-||-||1||1
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|ROM select||&DF||Write Only||-||-||0||-||-||-||-||-
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|Printer port||&EF||Write Only||-||-||-||0||-||-||-||-
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|PPI Port A||&F4||Read/Write||-||-||-||-||0||-||0||0
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|PPI Port B||&F5||Read/Write||-||-||-||-||0||-||0||1
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|PPI Port C||&F6||Read/Write||-||-||-||-||0||-||1||0
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|PPI Control||&F7||Read/Write||-||-||-||-||0||-||1||1
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|FDC||&F8-&FB||Read/Write||-||-||-||-||-||0||-||-
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|}
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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
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== I/O Ports ==
 
== I/O Ports ==
  
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{|{{Prettytable|width: 700px; font-size: 2em;}}
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{| class="wikitable"
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|'''I/O'''||'''Decoded as'''||'''Port'''||'''Read'''||'''Write'''
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!I/O
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!Decoded as
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!Port
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!Read
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!Write
 
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|#7FXX||%01xxxxxx xxxxxxxx||[[Gate Array]]||-||Write
 
|#7FXX||%01xxxxxx xxxxxxxx||[[Gate Array]]||-||Write
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* 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.
 
* 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.
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* Bit14 of the PAL selection address must be at 1 on CPCs equipped with CRTCs 0/1/2. It can be at 0 or 1 on CRTCs 3/4. For compatibility reasons, it is strongly advised to always set bit14 to 1 to select PAL.
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* As components use partial address decoding, it is therefore possible to send the same value to different components '''simultaneously''' by carefully using custom I/O ports.
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<br>
  
 
== Memory Mapped I/O Ports ==
 
== Memory Mapped I/O Ports ==
  
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{|{{Prettytable|width: 700px; font-size: 2em;}}
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{| class="wikitable"
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|'''Mem'''||'''Decoded as'''||'''Port'''||'''Read'''||'''Write'''
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!Mem
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!Decoded as
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!Port
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!Read
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!Write
 
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|#4000-7FFF||%01xxxxxx xxxxxxxx||[[ASIC]] - CPC+/GX4000 registers|| Read || Write
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|#4000-7FFF||%01xxxxxx xxxxxxxx||ASIC - CPC+/GX4000 registers|| Read || Write
 
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|}
 
|}
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See the [[ASIC]] page for details.
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<br>
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==Related pages==
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*[[Arnold V specs]]
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*[[Arnold V Specs Revised]]
  
 
[[Category:Programming]] [[Category:CPC Internal Components]]
 
[[Category:Programming]] [[Category:CPC Internal Components]]

Latest revision as of 06:23, 4 September 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 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.
  • Bit14 of the PAL selection address must be at 1 on CPCs equipped with CRTCs 0/1/2. It can be at 0 or 1 on CRTCs 3/4. For compatibility reasons, it is strongly advised to always set bit14 to 1 to select PAL.
  • As components use partial address decoding, it is therefore possible to send the same value to different components simultaneously by carefully using custom I/O ports.


Memory Mapped I/O Ports

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

See the ASIC page for details.


Related pages

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