I²C Reserved and Common Addresses
Address	R/W	Function/Device
0000 - 000	0	General Call address ¹
0000 - 000	1	Start byte ²
0000 - 001	x	Reserved for the now obsolete C-Bus format ³
0000 - 010	x	Reserved for a different bus format ⁴
0000 - 011	x	Reserved for future purposes ⁵
0000 - 1xx	x	Reserved for future purposes
1111 - 1xx	x	Reserved for future purposes
1111 - 0xx	x	10-bit slave addressing mode ⁶
1x
0001 - 011	LTC3445 programable buck converter (A7/6 selectable)
0001 - aaa	TES1328 Smart nixie base address (0x0-0x7) (Dip switch set to 0aaa is base address) (Dip switch set to 11xx is digital clock master)
aaaa - aaa 0001 - 000 to 1110 - 111	TES1328 Smart nixie analog address: 111 devices max when the DIP switch is set to 10aa, where aa is the analog address on open DIP positions 1 and 0. Each analog input is divided into 11 bins of Vdd/12 volts.
2x
0010 - 0aa	^{LTC26xx DAC}
0010 - 1aa	^{LTC2481,3,5 ADC}
3x
0011 - xxx
4x
0100 - 0aa	^{LTC26xx DAC}
0100 - 1aa	^{LTC2481,3,5 ADC}
0100 - aaa	^{AD799x ADC (Addr=0-7) LTC1699 DAC}
5x
0101 - aaa	^{AD799x ADC (Addr=8-15)}
0101 - 011	LTC3445 programable buck converter (A7/6 selectable) X9118 digital pot
0101 - 1aa	AD528x digital pot
6x
0110 - 0aa	^{LTC26xx DAC}
0110 - ccc	^{Seiko S3590A RTC: ccc = commands embedded in the address}
7x
0111 - 0aa	^{SAA1064 4 digit LED driver}
0111 - aaa	^{JCL1562 I/O expander}
8x
1000 - 0aa	^{LTC26xx DAC}
9x
1001 - 000	^{MCP9800/02A0 Temp sensor}
1001 - 00a	^{ADS1000 ADC}
1001 - 011	LTC3445 programable buck converter (A7/6 selectable)
1001 - 101	^{MCP9800/02A5 Temp sensor TC74 Temp sensor standard address}
1001 - 110	^{PCA8550 EEPROM dip switch}
1001 - aaa	^{DS1721 Temp sensor LM75 Temp sensor MCP9802/03 Temp sensor SC16IS7x0 UART}
Ax
1010 - 001	^{PCF8563 RTC-calendar}
1010 - 0aa	^{ADC081C027 ADC (aa=00,01,11 only) LTC26xx DAC}
1010 - 100	^{ADC081C021 ADC}
1010 - aaa	^{CAT140xx supervisor SC16IS7x0 UART DS1845 digital pot}
101a - aaa	^{MAX7325 I/O expander (Output port addressing)}
Bx
1011 - 001	X4003,5 supervisor
Cx
1100 - 0aa	^{LTC26xx DAC}
1100 - aaa	PCA9532/CAT9532 LED dimmer/driver PCA9551 LED blinker
110a - aaa	MAX7235 I/O expander (Input port addressing)
Dx
1101 - 000	^{DS1338,40 RTC MAX6909-10,17 RTC}
1101 - 00a	^{DS1372 counter}
1101 - 011	LTC3445 programable buck converter (A7/6 selectable)
1101 - 111	^{ISL1208 RTC}
Ex
1110 - 0aa	^{LTC26xx DAC}

1. The general call address
This address is being used to access all devices on the bus which are capable of handling the general call and need this data. Devices which are capable of handling this general call but do not need it will not answer.

All bytes transferred after this address may or may not be taken in by the slaves that are responding to it. If no slave is acknowledging a transmitted byte, the operation is stopped by issuing a STOP on the bus.

The meaning of the general call address is specified in the 1st byte transmitted after this "general call". This first byte can contain the following information:

If the LSB is set to 0:

0000-0110 Reset and write programmable part of slave address. All devices who respond to this will reset and take in the programmable part of their address. This is done by re-reading the levels on the address select pins of the device (if any). This command can be used to reset an entire I2C system.

0000-0100 The same as above but without the reset . This can be useful if the state of the address select pins of a device are configurable. This way the device address will change.

If the LSB is set to 1:

xxxx-xxx1 This is a Hardware Call. If a device needs urgent attention from a master device without knowing which master it needs to turn to, it can use this call. This is a call "to whom it may concern". The device then embeds its own address into the message. This call means as much as: Please contact me, I need to be serviced. All masters will listen and the master that knows how to handle the device with the address transmitted will contact its slave and act appropriately.

2. The START address
This can be used between masters. A master which does not have an I2C interface in hardware but in software needs to monitor the bus all the time. Since this can require a lot of processing time, the START address was introduced. The masters can sample the bus at a low rate. As soon as they detect that the SDA line is low (it is held low for over 7 clock periods) it can switch to a higher sampling rate to detect the Start condition. This address is not followed by a stop condition but rather by a repeated start condition.

3/4. Non I²C Data
These addresses are used when data other than I²C data has to be transmitted over the bus.

5. Future Expansion
These addresses are for further expansion and are currently not allowed.

6. 10 Bit Addressing
See details in the section covering 10-bit addressing.