Datasheet

558
SAM9M10 [DATASHEET]
6355F–ATARM–12-Mar-13
Figure 32-10. Master Read with Multiple Data Bytes
32.8.6 Internal Address
The TWI interface can perform various transfer formats: Transfers with 7-bit slave address devices and 10-bit slave
address devices.
32.8.6.1 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 location 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 I
2
C fully-compatible devices. See Figure 32-12. See
Figure 32-11 and Figure 32-13 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.
In the figures below the following abbreviations are used:
N
AS DADR R DATA n A ADATA (n+1) A DATA (n+m)DATA (n+m)-1 PTWD
TXCOMP
Write START Bit
RXRDY
Write STOP Bit
after next-to-last data read
Read RHR
DATA n
Read RHR
DATA (n+1)
Read RHR
DATA (n+m)-1
Read RHR
DATA (n+m)
•S
Start
•Sr
Repeated Start
•P
Stop
•W
Write
•R
Read
•A
Acknowledge
•N
Not Acknowledge
• DADR
Device Address
• IADR
Internal Address