UM10204 Datasheet, PDF (17/64 Pages) NXP Semiconductors – I2C-bus specification and user manual

NXP Semiconductors
UM10204
I²C-bus specification and user manual
The START byte 0000 0001 (01h) can precede the 10-bit addressing in the same way as
for 7-bit addressing (see Section 3.1.15).
3.1.12 Reserved addresses
Two groups of eight addresses (0000 XXX and 1111 XXX) are reserved for the purposes
shown in Table 3.
Table 3. Reserved addresses
X = don’t care; 1 = HIGH; 0 = LOW.
Slave address
R/W bit Description
0000 000
0
general call address^[1]
0000 000
1
START byte^[2]
0000 001
X
CBUS address^[3]
0000 010
X
reserved for different bus format^[4]
0000 011
X
reserved for future purposes
0000 1XX
X
Hs-mode master code
1111 1XX
X
reserved for future purposes
1111 0XX
X
10-bit slave addressing
[1] The general call address is used for several functions including software reset.
[2] No device is allowed to acknowledge at the reception of the START byte.
[3] The CBUS address has been reserved to enable the inter-mixing of CBUS compatible and I²C-bus
compatible devices in the same system. I²C-bus compatible devices are not allowed to respond on
reception of this address.
[4] The address reserved for a different bus format is included to enable I²C and other protocols to be mixed.
Only I²C-bus compatible devices that can work with such formats and protocols are allowed to respond to
this address.
Assignment of addresses within a local system is up to the system architect who must
take into account the devices being used on the bus and any future interaction with other
conventional I²C-buses. For example, a device with seven user-assignable address pins
allows all 128 addresses to be assigned. If it is known that the reserved address is never
going to be used for its intended purpose, a reserved address can be used for a slave
address.
The I²C-bus committee coordinates allocation of I²C addresses. Further information can
be obtained from the NXP web site www.nxp.com/i2c.
3.1.13 General call address
The general call address is for addressing every device connected to the I²C-bus at the
same time. However, if a device does not need any of the data supplied within the general
call structure, it can ignore this address by not issuing an acknowledgment. If a device
does require data from a general call address, it acknowledges this address and behave
as a slave-receiver. The master does not actually know how many devices acknowledged
if one or more devices respond. The second and following bytes are acknowledged by
every slave-receiver capable of handling this data. A slave who cannot process one of
these bytes must ignore it by not-acknowledging. Again, if one or more slaves
acknowledge, the not-acknowledge will not be seen by the master. The meaning of the
general call address is always specified in the second byte (see Figure 16).
UM10204
User manual
All information provided in this document is subject to legal disclaimers.
Rev. 4 — 13 February 2012
© NXP B.V. 2012. All rights reserved.
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