The limited I/O address space is currently assigned as follows.

These are my address assignments. It is not an official list for all RCBus systems, although most are de facto standards. Most SC modules have tight address decoding and address selection jumpers, so they can be relocated to avoid conflicts.

I/O Address	Use
0x00 to 0x03	Digital I/O
0x00 to 0x03	Status LED #2 (active high) SC707 (80 pin module)
0x00	Digital I/O #1 SC129 (40+ pin module) SC605 (40 pin module) SC719 (80 pin module)
0x00	Front panel switches (RomWBW) Read only SC129 (40+ pin module) SC136 (40 pin low profile module) SC605 (40 pin module) SC719 (80 pin module)
0x00	Front panel status LEDs (RomWBW) Write only SC129 (40+ pin module) SC134 (40 pin low profile module) SC601 (40 pin module) SC605 (40 pin module) SC719 (80 pin module)
0x01	Digital I/O #2 SC129 (40+ pin module) SC605 (40 pin module) SC719 (80 pin module)
0x04 to 0x05	PWM channels #1 and #2 SC731 (80 pin module)
0x06 to 0x07	Servo channels #1 and #2 SC609 (40 pin module) SC732 (80 pin module)
0x08 to 0x0B	Status LED #1 (active low) Write only SC114 (40 pin motherboard) SC150 (40 pin low profile module) SC151 (40 pin low profile module) SC707 (40 pin module) SC708 (80 pin module)
0x08 to 0x09	TMSEMU3 terminal & graphics module in Tatung Einstein compatible mode
0x0C	I2C bus master can share this address with RTC SC137 (40 pin low profile module) SC608 (40 pin module) SC704 (80 pin module)
0x0C	Real time clock DS1302 (for Z180 CPU) can share this address with I2C SC606 (40 pin module) SC727 (80 pin module)
0x0C	I2C + RTC + SPI SC126 (80 pin motherboard)
0x0D	LED output port Write only SC129 (40+ pin module) SC134 (40 pin low profile module) SC126 (80 pin motherboard) SC605 (40 pin module) SC719 (80 pin module)
0x0E	Status LED #1 (active low) Write only SC130 (40 pin motherboard) SC131 (pocket-sized computer)
0x0F	Not assigned in SC range
0x10 to 0x17	Compact Flash #1 SC145 (40 pin low profile module) SC604 (40 pin module) SC715 (80 pin module) SC720 (80 pin motherboard) SC729 (80 pin module)
0x18 to 0x1B	Reserved in SC range
0x20 to 0x27	PPIDE / Hard disk RC2014
0x20 to 0x23	Bit-bang serial RTS SC114 (40 pin motherboard) SC708 (80 pin module module)
0x20 to 0x23	ROM bank select A15 SC151 (40 pin low profile module) SC707 (80 pin module) optional
0x20	I2C bus master (alternate address) SC137 (40 pin low profile module) SC608 (40 pin module) SC704 (80 pin module)
0x24 to 0x27	Not assigned in SC range
0x28 to 0x2B	ROM bank select A16 SC151 (40 pin low profile module) SC707 (80 pin module) optional
0x28 to 0x2B	Bit-bang serial TXD Write only SC114 (40 pin motherboard) SC708 (80 pin module)
0x2C to 0x2F	Not assigned in SC range
0x30 to 0x3F	RAM/ROM select 64k RC2014
0x30 to 0x33	RAM bank select A16 Write only SC114 (40 pin motherboard) SC150 (40 pin low profile module) SC707 (80 pin module)
0x34 to 0x37	Not assigned in SC range
0x38 to 0x3B	RAM/ROM select (128k Z80 systems) Write only SC114 (40 pin motherboard) SC150 (40 pin low profile module) SC151 (40 pin low profile module) SC707 (80 pin module) SC708 (80 pin module)
0x3C to 0x3D	USB device #2 (CH375/376) RC2014
0x3E to 0x3F	USB device #1 (CH375/376) RC2014
0x40 to 0x41	Serial ACIA #2 (one serial port) SC139 (40 pin low profile module) SC610 (40 pin module) SC705 (80 pin module)
0x42 to 0x47	Not assigned in SC range
0x48 to 0x49	Floppy disk FLOCK v2 (also 0x50/1 and 0x58/9)
0x4A to 0x4F	Not assigned in SC range
0x50 to 0x51	Floppy disk FLOCK v2 (also 0x48/9 and 0x58/9)
0x52 to 0x57	Not assigned in SC range
0x58 to 0x59	Floppy disk FLOCK v2 (also 0x48/9 and 0x50/1)
0x5A to 0x5F	Not assigned in SC range
0x60 to 0x6F	Sound (AY chip) RC2014
0x68 to 0x6B	Z80 PIO #1 SC103 (40+ pin module) SC717 (80 pin module)
0x69	Micro SD card (PIO mode) SC611 (40 pin module)
0x6C to 0x6F	See sound (AY chip)
0x70 to 0x7F	Memory bank select (16kB banks) RC2014
0x70 to 0x77	Not assigned in SC range
0x78 to 0x79	Memory bank select (32kB banks) SC602 (40 pin module) SC714 (80 pin module) SC720 (80 pin motherboard SC730 (80 pin module)
0x80 to 0xBF	ACIA (one serial port) RC2014 Yes, that really is 0x80 to 0xBF
0x80 to 0x87	Z80 SIO (two serial ports) RC2014
0x80 to 0x87	UART #1 16Cxxx (one serial port) RC2014
0x80 to 0x83	Z80 SIO #1 (two serial ports) SC104 (40+ pin module) SC110 (40+ pin module) SC603 (40 pin module) SC716 (80 pin module) SC720 (80 pin motherboard) SC725 (80 pin module)
0x80 to 0x81	Serial ACIA #1 (one serial port) SC139 (40 pin low profile module) SC610 (40 pin module) SC705 (80 pin module)
0x84 to 0x87	Z80 SIO #2 (two serial ports) SC104 (40+ pin module) SC603 (40 pin module) SC716 (80 pin module)
0x88 to 0x8F	UART #2 16Cxxx (one serial port) RC2014
0x88 to 0x8B	Z80 CTC #1 SC102 (40+ pin module) SC110 (40+ pin module) SC718 (80 pin module) SC725 (80 pin module)
0x8C to 0x8F	Z80 CTC #2 SC102 (40+ pin module) SC718 (80 pin module)
0x90 to 0x97	Not assigned in SC range
0x98 to 0x99	TMSEMU3 terminal & graphics module in MSX compatible mode
0x9A to 0x9F	Not assigned in SC range
0xA0 to 0xA7	UART #3 16Cxxx (one serial port) RC2014
0xA8 to 0xAF	UART #4 16Cxxx (one serial port) RC2014
0xB0 to 0xBD	Not assigned in SC range
0xBE to 0xBF	TMSEMU3 terminal & graphics module in Tatung Einstein compatible mode
0xC0 to 0xFF	Z180 CPU internal registers SC126 (80 pin module) SC130 (40 pin module) SC722 (80 pin module)
0xC0	Real time clock DS1302 (for Z80 CPU) SC606 (40 pin module) SC727 (80 pin module)
0xDA to 0xDB	LCD driver module (alpha-numeric) RC2014 Alternative addresses: 0xAA/AB, 0x5A/5B, 0x2A/2B