I/O Port Summary

This is a list of all known I/O ports of the Amstrad CPC, including all Peripherals. For a list showing only the built-in standard addresses see Default I/O Port Summary. The original list of I/O ports was taken from the FutureOS handbook.

I/O Port Summary

Note: While most of these devices can be reached via a range of addresses due to the partial address decoding, code should never use any address other than the canonical one (all 'x'/don't care positions filled by 1's). Otherwise multiple devices will be enabled simultaneously, which is unlikely to be what you want.

I/O	Decoded as	Port	Read	Write
#1C00	%x0xxxx00 xxxxxxxx	Dk'tronics Lightpen faulty mirror of #BCXX CRTC Index	-	Write
#1F00	%x0xxxx11 xxxxxxxx	Dk'tronics Lightpen faulty mirror of #BFXX CRTC Data In	Read	-
#78XX	%0xxxx000 xxxxxxxx	4Mb Memory extension	-	Write
#79XX	%0xxxx001 xxxxxxxx	4Mb Memory extension	-	Write
#7AXX	%0xxxx010 xxxxxxxx	4Mb Memory extension	-	Write
#7BXX	%0xxxx011 xxxxxxxx	4Mb Memory extension	-	Write
#7CXX	%0xxxx100 xxxxxxxx	4Mb Memory extension	-	Write
#7CXX	%0xxxxx00 xxxxxxxx	Aleste 520EX RAM Mapper page 0 (extended "Gate Array 3")	Read	Write
#7DXX	%0xxxx101 xxxxxxxx	4Mb Memory extension	-	Write
#7DXX	%0xxxxx01 xxxxxxxx	Aleste 520EX RAM Mapper page 1 (extended "Gate Array 3")	Read	Write
#7EXX	%0xxxx110 xxxxxxxx	4Mb Memory extension	-	Write
#7EXX	%0xxxxx10 xxxxxxxx	Aleste 520EX RAM Mapper page 2 (extended "Gate Array 3")	Read	Write
#7EXX	%0xxxxxx0 xxxxxxxx	Y-MEM 512K RAM Expansion part	Read	Write
#7FXX	%0xxxx111 xxxxxxxx	4Mb Memory extension	-	Write
#7FXX	%0xxxxx11 xxxxxxxx	Aleste 520EX RAM Mapper page 3 (extended "Gate Array 3")	Read	Write
#7FXX	%0xxxxxx1 xxxxxxxx	X-MEM 512K RAM Expansion part	Read	Write
#7FXX	?	Dk'tronics memory expansion	-	Write
#7FXX	?	Dobbertin Memory Expansion	-	Write
#7FXX	%01xxxxxx xxxxxxxx	Gate Array	-	Write
#7FXX	%0xxxxxxx xxxxxxxx	PAL16L8 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 (as decoded within CPC664, CPC6128, 464+, 6128+, decoding in ROM expansions may be different)	-	Write
#ECXX	%xxx0xx00 xxxxxxxx	KC Compact CIO Port B (timer)	Read	Write
#EDXX	%xxx0xx01 xxxxxxxx	KC Compact CIO Port C (timer)	Read	Write
#EEXX	%xxx0xx10 xxxxxxxx	KC Compact CIO Control	Read	Write
#EEXX	%xxx0xxx0 xxxxxxxx	Aleste 520EX USART 8251 (RS232/Mouse) Data	Read	Write
#EFXX	%xxx0xx11 xxxxxxxx	KC Compact CIO Port A (Bi-drectional Printer Port)	Read	Write
#EFXX	%xxx0xxx1 xxxxxxxx	Aleste 520EX USART 8251 (RS232/Mouse) Control/Status	Read	Write
#EFXX	%xxx0xxxx xxxxxxxx	Printer Port	-	Write
#F0E0	?	Draysoft Doubler External Tape Data Input (Bit5)	Read	-
#F4XX	%xxxx0x00 xxxxxxxx	8255 PIO Port A (PSG Data)	Read	Write
#F5XX	%xxxx0x01 xxxxxxxx	8255 PIO Port B (Vsync,PrnBusy,Tape,etc.)	Read	-
#F6XX	%xxxx0x10 xxxxxxxx	8255 PIO Port C (KeybRow,Tape,PSG Control)	-	Write
#F7XX	%xxxx0x11 xxxxxxxx	8255 PIO Control-Register	-	Write
#F880-#F88F	%1111100x 1000xxxx	PlayCity Expansion CTC channels and YMZ data	-	Write
#F890-#F89F	%1111100x 1--1xxxx	MultiPlay Expansion (mirror port, use #F9xx)	Read	-
#F8A0-#F8AF	%11111000 1010xxxx	X-CPC ClockPort RTC	Read	Write
#F8B0	?	Vidi-CPC Video-Digitiser, CRTC Index	?	Write
#F8B1	?	Vidi-CPC Video-Digitiser, CRTC Data	?	Write
#F8DC	?	CPCI Serial Interface MC6850 Control/Status	Read	Write
#F8DD	?	CPCI Serial Interface MC6850 Data	Read	Write
#F8E0	?	DHCP MIDI Interface	Read	Write
#F8E0	%11111000 11100000	Schneider RS232 Interface Z80-STI Indirect Data Register	Read	Write
#F8E1	%11111000 11100001	Schneider RS232 Interface Z80-STI General Purpose I/O Data Register	Read	Write
#F8E2	%11111000 11100010	Schneider RS232 Interface Z80-STI Interrupt Pending Register B (unused)	Read	Write
#F8E2	?	Dobbertin Eprommer 4003	?	?
#F8E3	%11111000 11100011	Schneider RS232 Interface Z80-STI Interrupt Pending Register A (unused)	Read	Write
#F8E3	?	Dobbertin Eprommer 4003	?	?
#F8E4	%11111000 11100100	Schneider RS232 Interface Z80-STI Interrupt in-Service Register B (unused)	Read	Write
#F8E4	?	Dobbertin Eprommer 4003	?	?
#F8E5	%11111000 11100101	Schneider RS232 Interface Z80-STI Interrupt in-Service Register A (unused)	Read	Write
#F8E6	%11111000 11100110	Schneider RS232 Interface Z80-STI Interrupt Mask Register B (unused)	Read	Write
#F8E6	?	Port A - IDE8255	?	?
#F8E7	%11111000 11100111	Schneider RS232 Interface Z80-STI Interrupt Mask Register A (unused)	Read	Write
#F8E7	?	Port C - IDE8255	?	?
#F8E8	%11111000 11101000	Schneider RS232 Interface Z80-STI Indirect Index and Interrupt Vector Register	Read	Write
#F8E8	?	Music Machine Interrupt Sel	-	Write
#F8E9	%11111000 11101001	Schneider RS232 Interface Z80-STI Timers A and B Control Register (unused)	Read	Write
#F8EA	%11111000 11101010	Schneider RS232 Interface Z80-STI Timer B Data Register (unused)	Read	Write
#F8EB	%11111000 11101011	Schneider RS232 Interface Z80-STI Timer A Data Register (unused)	Read	Write
#F8EC	%11111000 11101100	Schneider RS232 Interface Z80-STI USART Control Register	Read	Write
#F8EC	?	Music Machine ACIA Control	-	Write
#F8ED	?	Music Machine ACIA Data Write	-	Write
#F8ED	%11111000 11101101	Schneider RS232 Interface Z80-STI Receiver Status Register	Read	Write
#F8EE	?	Music Machine ACIA Status	Read	-
#F8EE	%11111000 11101110	Schneider RS232 Interface Z80-STI Transmitter Status Register	Read	Write
#F8EF	%11111000 11101111	Schneider RS232 Interface Z80-STI USART Data Register	Read	Write
#F8EF	?	Music Machine ACIA Data Read	Read	-
#F8FX	%xxxxx0xx 1111NNNx	Maplins 8bit Input Port and Maplins Weather Satellite Receiver	Read	-
#F8F0	?	Music Machine DAC Write	-	Write
#F8F2	?	EMR MIDI Interface	-	Write
#F8F2	?	Dobbertin Eprommer 4003	Read	Write
#F8F2	?	EMR MIDI Interface	Read	Write
#F8F4	?	Music Machine ADC Read	Read	-
#F8F5	?	ARA Video Digitizer - Read Sync Signal (bit0)	Read	-
#F8F8	?	Music Machine ADC Start	-	Write
#F8F8	?	ANTA 64K Memory Expansion ANTA 64k.3 latch	Read	Write
#F8FE	%11111000 11111110	Z-MEM Software Memory Configuration	-	Write
#F8FF	%1111100x 111xxxxx	CPCISA control port	-	Write
#F8FF	%xxxxx0xx 111111xx	Peripheral Soft Reset (MC_BOOT_PROGRAM and MC_START_PROGRAM do OUT [F8FF],FF)	-	Write
#F980-#F98F	%1111100x 1000xxxx	PlayCity Expansion CTC channels (mirror) and YMZ registers	-	Write
#F990-#F99F	%1111100x 1--1xxxx	MultiPlay Expansion	Read	-
#F9A0-#F9AF	%11111001 1010xxxx	X-CPC ClockPort SPR	Read	Write
#F9B0	?	Vidi-CPC Video-Digitiser, Config (W) and Capture Data (R)	Read	Write
#F9D0	%11111000 11010000	SwinSID part of SONIQUE Sound Board WIP by DaDMaN SwinSID1 + SwinSID2 DATA (MONO Mode / 3 Channels)	-	Write
#F9D1	%11111000 11010001	SwinSID part of SONIQUE Sound Board WIP by DaDMaN SwinSID1 (LEFT) DATA (STEREO Mode / 6 Channels)	-	Write
#F9D2	%11111000 11010010	SwinSID part of SONIQUE Sound Board WIP by DaDMaN SwinSID2 (RIGHT) DATA (STEREO Mode / 6 Channels)	-	Write
#F9DC	?	Panda Electronics Communications Interface Unit PPI Port A - 8bit Printer data	Read	Write
#F9DD	?	Panda Electronics Communications Interface Unit PPI Port B - 8bit general purpose I/O port	Read	Write
#F9DE	?	Panda Electronics Communications Interface Unit PPI Port C - Handshake (bit0=Strobe.out, Bit5=Busy.in)	Read	Write
#F9DF	?	Panda Electronics Communications Interface Unit PPI Control - 8bit Printer data	-	Write
#F9E6	?	Port B - IDE8255	?	?
#F9E7	?	RS Port - IDE8255	?	?
#F9F5	?	ARA Video Digitizer - Reset 10bit Config Value	-	Write
#F9F7	?	Hegotron grafpad II	?	?
#F9FC - #F9FE	?	Otten & Fecht 1 MB RAM-Disc	Read	Write
#F9FF	?	Hegotron grafpad II	?	?
#FA7E	%xxxxx0x0 0xxxxxxx	Floppy Motor Control (for 765 FDC)	-	Write
#FABC	%xxxxx0x0 10xxxx00	Aleste 520EX EXTPORT with CS53: Forward PPI Port A to 8253 Timer 0	-	Write
#FABD	%xxxxx0x0 10xxxx01	Aleste 520EX EXTPORT with CS53: Forward PPI Port A to 8253 Timer 1	-	Write
#FABE	%xxxxx0x0 10xxxx10	Aleste 520EX EXTPORT with CS53: Forward PPI Port A to 8253 Timer 2	-	Write
#FABF	%xxxxx0x0 10xxxx11	Aleste 520EX EXTPORT with CS53: Forward PPI Port A to 8253 Control	-	Write
#FABF	%xxxxx0x0 10xxxxxx	Aleste 520EX EXTPORT (config for internal hardware)	-	Write
#FAD0	%11111010 11010000	SwinSID part of SONIQUE Sound Board WIP by DaDMaN Select SID (1&2) Register MONO mode	-	Write
#FAD1	%11111010 11010001	SwinSID part of SONIQUE Sound Board WIP by DaDMaN Select SID1 Register	-	Write
#FAD2	%11111010 11010010	SwinSID part of SONIQUE Sound Board WIP by DaDMaN Select SID2 Register	-	Write
#FADC	?	Amstrad Serial Interface Z80-SIO / DART port A Data Register	Read	Write
#FADC	?	MHT Ingenieros RS232 para Amstrad 8251 USART data	Read	Write
#FADD	?	Amstrad Serial Interface Z80-SIO / DART port A Control Reg.	Read	Write
#FADD	?	MHT Ingenieros RS232 para Amstrad 8251 USART control/status	Read	Write
#FADE	?	Amstrad Serial Interface Z80-SIO / DART port B Data Register	Read	Write
#FADF	?	Amstrad Serial Interface Z80-SIO / DART port B Control Reg.	Read	Write
#FADF	?	Cirkit serial interface 8251 UART data register	Read	Write
#FAE6	?	Port A - IDE8255	?	?
#FAE7	?	Port C - IDE8255	?	?
#FAEE	?	Amstrad SSA-1 Speech Synthesizer (faulty mirror used by included RSX driver)	Read	Write
#FAEF	%xxxxx0x0 xxx0xxxx	Kempston Mouse - Mouse Buttons	Read	-
#FAF5	?	ARA Video Digitizer - Read Capture Data	Read	-
#FAF5	?	ARA Video Digitizer - Increment 10bit Config Value	-	Write
#FB7E	%xxxxx0x1 0xxxxxx0	765 FDC (internal) Status Register	Read	-
#FB7F	%xxxxx0x1 0xxxxxx1	765 FDC (internal) Data Register	Read	Write
#FBBD	%xxxxx0xx x0xxxx0x	Ram select mode Vortex SP512	?	Write
#FBDC	?	Amstrad Serial Interface 8253 Timer counter 0	Read	Write
#FBDC	?	MHT Ingenieros RS232 para Amstrad 8253 timer 0 (transmit baudrate)	Read	Write
#FBDD	?	Amstrad Serial Interface 8253 Timer counter 1	Read	Write
#FBDD	?	MHT Ingenieros RS232 para Amstrad 8253 timer 1 (receive baudrate)	Read	Write
#FBDE	?	Amstrad Serial Interface 8253 Timer counter 2	Read	Write
#FBDE	?	MHT Ingenieros RS232 para Amstrad 8253 timer 2 (used as 1ms timer)	Read	Write
#FBDF	?	Amstrad Serial Interface 8253 Timer Modus Select	-	Write
#FBDF	?	MHT Ingenieros RS232 para Amstrad 8253 timer 0-2 control	-	Write
#FBDF	?	Cirkit serial interface 8251 UART status/control register	Read	Write
#FBxx+0	?	CPCI Real Time Clock Index (DIY)	-	Write
#FBxx+1	?	CPCI Real Time Clock Data (DIY)	Read	Write
#FBE0	?	Dk'tronics Real Time Clock - Z80 PIO Port A Data (HD146818P RTC Data bus)	Read	Write
#FBE0	?	Dobbertin Harddisc Data Port	Read	Write
#FBE1	?	Dk'tronics Real Time Clock - Z80 PIO Port B Data (General Purpose 8bit I/O Port)	Read	Write
#FBE1	?	Dobbertin Harddisc Status, Reset	Read	Write
#FBE2	?	Dk'tronics Real Time Clock - Z80 PIO Port A Control	?	Write
#FBE2	?	Dobbertin Harddisc Select, Configuration	Read	Write
#FBE3	?	Dk'tronics Real Time Clock - Z80 PIO Port B Control	?	Write
#FBE3	?	Dobbertin Harddisc DMA, Interrupt	Read	Write
#FBE4	?	Dobbertin Harddisc Reset	Read	Write
#FBE6	?	Port B - IDE8255	?	?
#FBE7	?	RS Port - IDE8255	?	?
#FBE7	?	ACU Real Time Clock (DIY) Z80-PIO Data In/Out Port A	Read	Write
#FBE8	?	Dk'tronics Real Time Clock "4bit latch" (details unknown)	?	Write
#FBE8	?	KDS RS232 8253 Timer0 (RX Clock)	Read	Write
#FBE9	?	KDS RS232 8253 Timer1 (TX Clock)	Read	Write
#FBEA	?	KDS RS232 8253 Timer2 (not used)	Read	Write
#FBEB	?	KDS RS232 8253 Timer Control	-	Write
#FBEC	?	KDS RS232 6850 (reversed bit-order) Control	-	Write
#FBEC	?	PDS development system Z80 PIO Port A Data (8bit data to/from PC)	Read	Write
#FBED	?	KDS RS232 6850 (reversed bit-order) TX Data	-	Write
#FBED	?	PDS development system Z80 PIO Port B Data (handshake to/from PC)	Read	Write
#FBEE	?	PDS development system Z80 PIO Port A Control	?	Write
#FBEE	?	Amstrad SSA-1 Speech Synthesizer	Read	Write
#FBEE	?	LambdaSpeak Speech Synthesizer	Read	Write
#FBEE	%xxxxx0x1 xxx0xxx0	Kempston Mouse - 8bit X position	Read	-
#FBEE	?	KDS RS232 6850 (reversed bit-order) Status	Read	-
#FBEF	?	PDS development system Z80 PIO Port B Control	?	Write
#FBEF	%xxxxx0x1 xxx0xxx1	Kempston Mouse - 8bit Y position	Read	-
#FBEF	?	KDS RS232 6850 (reversed bit-order) RX Data	Read	-
#FBEF	?	ACU Real Time Clock (DIY) Z80-PIO Data In/Out Port B	Read	Write
#FBF0 - #FBFF	?	Otten & Fecht 1 MB RAM-Disc	Read	Write
#FBF0	%xxxx1011 1111xxxx	AMRAM2	-	Write
#FBF0	%xxxxx011 1111xxx0	AMSSIO Serial Interface MC6850 Control/Status Register	Read	Write
#FBF1	%xxxxx011 1111xxx1	AMSSIO Serial Interface MC6850 Data Register	Read	Write
#FBF5	?	ARA Video Digitizer - Invoke Video Capture	-	Write
#FBF6	?	Vortex Disc Drives 765 FDC (Vortex,ext) Status Register	Read	-
#FBF7	?	Vortex Disc Drives 765 FDC (Vortex,ext) Data Register	Read	Write
#FBF7	?	ACU Real Time Clock (DIY) Z80-PIO Configure Port A	Read	Write
#FBF8	%11111011 11111000	8bit Printer Port (Amstrad Action) Strobe/Busy	Read	Write
#FBF9	%11111011 11111001	8bit Printer Port (Amstrad Action) Data	-	Write
#FBFE	?	Magnum Light Phaser	-	Write
#FBFE	?	Dart Scanner for DMP-Printers	Read	?
#FBFE	?	Dk'tronics Speech Synthesizer	Read	Write
#FBFE	%xxxxxxxx 11111110	TMPI speech synthesizer Data Register		Write
#FBFF	%xxxxxxxx 11111111	TMPI speech synthesizer Command/Status Register	Read	Write
#FBFF	?	ACU Real Time Clock (DIY) Z80-PIO Configure Port B	Read	Write
#FC00 - #FDFF	%1111110x xxxxxxxx	CPCISA 16bits mode high byte latch	Read	Write
#FC00	?	M4 Board ACK/KICK	-	Write
#FC5C	?	French DIY Dual Port RS232 - Baudrate Selection	-	Write
#FC7C	?	French DIY Dual Port RS232 - Z80-SIO Channel A Data	Read	Write
#FC7D	?	French DIY Dual Port RS232 - Z80-SIO Channel A Control/Status	Read	Write
#FC7E	?	French DIY Dual Port RS232 - Z80-SIO Channel B Data	Read	Write
#FC7F	?	French DIY Dual Port RS232 - Z80-SIO Channel B Control/Status	Read	Write
#FCE6	?	Port A - IDE8255	Read	Write
#FCE7	?	Port C - IDE8255	Read	Write
#FD00 - #FD3F	%11111101 00xxxxxx	SYMBiFACE II	Read	Write
#FD08 - #FD0F	%11111101 00001xxx	X-MASS 2.5" 44-pin IDE interface / DOM / CF adapter (SYMBiFACE II compatible)	Read	Write
#FD40 - #FD4F	%11111101 0100xxxx	SYMBiFACE III	Read	Write
#FD80 - #FD87	%11111101 10000xxx	CPC-CPLink - FIFO Interface card for Co-processors, incl. Raspberry Pi	Read	Write
#FDE6	?	Port B - IDE8255	Read	Write
#FDE7	?	RS Port - IDE8255	Read	Write
#FE00	?	M4 Board Data	-	Write
#FE00 - #FFFF	%1111111x xxxxxxxx	CPCISA I/O access (low byte)	Read	Write
#FE80 - #FE81	%11111110 1000000x	Albireo CH376 controller	Read	Write
#FE82	%11111110 10000010	Nova RTC & NVRAM	-	Write
#FE84 - #FEA7	%11111110 10xxx1xx	Willy Future use or multi-soundchip	-	-
#FEAC - #FEAD	%11111110 101011xx	Willy S2P Dream SAM2965 MIDI synthetizer	Read	Write
#FEB0 - #FEB7	%11111110 10110xxx	Albireo serial port	Read	Write
#FEBC - #FEBF	%11111110 101111xx	Willy OPL3	-	Write
#FEE6	?	Port A - IDE8255	Read	Write
#FEE7	?	Port C - IDE8255	Read	Write
#FEE8	%11111110 1110100x	Multiface II - Enable Multiface II ROM/RAM	-	Write
#FEEA	%11111110 1110110x	Multiface II - Disable Multiface II ROM/RAM	-	Write
#FEF0 - #FEF7	%11111110 11110xxx	CPC-CompactFlash - IDE registers	Read	Write
#FEF0 - #FEF7	%11111110 11110xxx	uIDE 16 - IDE registers	Read	Write
#FF00 - #FFFF	%11111111 xxxxxxxx	AMSDAP (Amstrad MSx aDAPter, MSX-to-CPC I/O hardware interface (MSX ports #00-#ff)	Read	Write
#FF20 - #FF27	%11111111 00100xxx	MP3MSX (MP3 player) via AMSDAP	Read	Write
#FF20 - #FF27	%11111111 00100xxx	SE-ONE (MP3 player, FM radio receiver, USB master interface) via AMSDAP	Read	Write
#FF60 - #FF6F	%11111111 0110xxxx	CPC V9990 PowerGraph (upcoming graphic card based on the Graphics 9000 for the MSX)	Read	Write
#FFXX	%11111111 xxxxxxxx	CPC Booster (XX=#00..#28 are used now)	Read	Write
#FFXX	%11111111 xxxxxxxx	Amdrum (unsigned 8bit DAC)	-	Write
#FFE6	?	Port B - IDE8255	Read	Write
#FFE7	?	RS Port - IDE8255	Read	Write

Memory Mapped I/O Ports

Mem	Decoded as	Port	Read	Write
#4000-7FFF	%01xxxxxx xxxxxxxx	ASIC - CPC+/GX4000 registers	Read	Write
#C00?	%11000000 0000000x	Dobbertin Smart Watch data read (A0=data)	Read	-
#C00?	%11000000 0000000x	Dobbertin Smart Watch data write (A0=data)	Read	-

More Ports

Some more I/O addresses (which aren't included in the above list) are here:

• Schneiderware Summary
• CPCISA

Other I/O Ports

A number of peripherals connect to the joystick/printer ports, and so, they do not include "own" I/O addresses. This includes hardware other than joysticks/printers - for example, mice, robots, audio devices, and simple network adapters. For a more complete list, see corresponding sections on Digital Joystick and Printer Port pages.

Aside from I/O addresses, there are some other important I/O signals, for example: NMI or INT.