•
Status register (STATUS)
•
Data register (DATA)
•
Address register (ADDR)
Optional PAC Write-Protection is denoted by the "PAC Write-Protection" property in each individual
register description.
Write-protection does not apply to accesses through an external debugger.
Related Links
PAC - Peripheral Access Controller
on page 50
34.5.9. Analog Connections
Not applicable.
34.6. Functional Description
34.6.1. Principle of Operation
The I
2
C interface uses two physical lines for communication:
•
Serial Data Line (SDA) for packet transfer
•
Serial Clock Line (SCL) for the bus clock
A transaction starts with the I
2
C master sending the start condition, followed by a 7-bit address and a
direction bit (read or write to/from the slave).
The addressed I
2
C slave will then acknowledge (ACK) the address, and data packet transactions can
begin. Every 9-bit data packet consists of 8 data bits followed by a one-bit reply indicating whether the
data was acknowledged or not.
If a data packet is not acknowledged (NACK), whether by the I
2
C slave or master, the I
2
C master takes
action by either terminating the transaction by sending the stop condition, or by sending a repeated start
to transfer more data.
The figure below illustrates the possible transaction formats and
the transaction symbols. These symbols will be used in the following descriptions.
Figure 34-2. Basic I
2
C Transaction Diagram
SDA
SCL
S
ADDRESS
R/W
ACK
DATA
ACK
DATA
ACK/NACK
6..0
7..0
7..0
P
S
ADDRESS
R/W
A
DATA
P
A
DATA
A/A
Direction
Address Packet
Data Packet #0
Data Packet #1
Transaction
Atmel SAM L22G / L22J / L22N [DATASHEET]
Atmel-42402E-SAM L22G / L22J / L22N_Datasheet_Complete-07/2016
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