Atmel SAM4L-EK Atmel ATSAM4L-EK ATSAM4L-EK Data Sheet

42023E–SAM–07/2013

Figure 28-2. Application Block Diagram 

In order to use this module, other parts of the system must be configured correctly, as described
below.

 TWD and TWCK are bidirectional lines, connected to a positive supply voltage via a current
source or pull-up resistor (see 

). When the bus is free, both lines are

high. The output stages of devices connected to the bus must have an open-drain or open-col-
lector to perform the wired-AND function.

 TWD and TWCK pins may be multiplexed with I/O Controller lines. To enable the TWIS, the
user must perform the following steps:

• Program the I/O Controller to:

– Dedicate  TWD, TWCKas peripheral lines.

– Define  TWD, TWCKas open-drain.

If the CPU enters a sleep mode that disables clocks used by the TWIS, the TWIS will stop func-
tioning and resume operation after the system wakes up from sleep mode. The TWIS is able to
wake the system from sleep mode upon address match, see 

Host with

TWI

Interface

TWD

TWCK

Atmel TWI

serial EEPROM

I²C RTC

I²C LCD

controller

Slave 1

Slave 2

Slave 3

VDD

I²C temp.

sensor

Slave 4

Rp: Pull up value as given by the I²C Standard

Rp

Rp

I/O Lines Description

TWD

Two-wire Serial Data

Input/Output

TWCK

Two-wire Serial Clock

Input/Output