
682
SAM4CP [DATASHEET]
43051E–ATPL–08/14
Figure 34-11. Master Read Wait State with Multiple Data Bytes
34.7.3.6 Internal Address
The TWI interface can perform transfers with 7-bit slave address devices and 10-bit slave address devices.
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, e.g. within a memory page location in a serial memory. 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 I
2
C fully-compatible devices. See
Figure 34-13
. See
Figure 34-12
and
Figure 34-14
for
Master Write operation with internal address.
The three internal address bytes are configurable through the Master Mode register (TWI_MMR).
If the slave device supports only a 7-bit address, i.e., no internal address, IADRSZ must be set to 0.
Table 34-6
shows the abbreviations used in
Figure 34-12
and
Figure 34-13
.
A
DATA n
A
S
DADR
W
DATA n+1
A
P
DATA n+2
A
TXCOMP
RXRDY
Read RHR (Data n)
STOP command performed
(by writing in the TWI_CR)
TWD
TWCK
Read RHR (Data n+1)
Read RHR (Data n+2)
Clock Wait State
Table 34-6.
Abbreviations
Abbreviation
Definition
S
Start
Sr
Repeated Start
P
Stop
W
Write
R
Read
A
Acknowledge
NA
Not Acknowledge
DADR
Device Address
IADR
Internal Address