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AT32UC3B
19.10.7.1
7-bit Slave Addressing
When Addressing 7-bit slave devices, the internal address bytes are used to perform random
address (read or write) accesses to reach one or more data bytes, within a memory page loca-
tion in a serial memory, for example. When performing read operations with an internal address,
the TWI performs a write operation to set the internal address into the slave device, and then
switch to Master Receiver mode. Note that the second start condition (after sending the IADR) is
sometimes called “repeated start” (Sr) in I2C fully-compatible devices. See
Figure 19-12. See
The three internal address bytes are configurable through the Master Mode register (MMR).
If the slave device supports only a 7-bit address, i.e. no internal address, IADRSZ must be set to
0.
n the figures below the following abbreviations are used:I
Figure 19-11. Master Write with One, Two or Three Bytes Internal Address and One Data Byte
S
Start
Sr
Repeated Start
P
Stop
W
Write
R
Read
A
Acknowledge
N
Not Acknowledge
DADR
Device Address
IADR
Internal Address
S
DADR
W
A
IADR(23:16)
A
IADR(15:8)
A
IADR(7:0)
A
DATA
A
P
S
DADR
W
A
IADR(15:8)
A
IADR(7:0)
A
P
DATA
A
IADR(7:0)
A
P
DATA
A
S
DADR
W
TWD
Three bytes internal address
Two bytes internal address
One byte internal address
TWD