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

42023E–SAM–07/2013

Figure 27-2. 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.

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

• Program the I/O Controller to:

– Dedicate  TWD, TWCK as peripheral lines.

– Define  TWD, TWCK as open-drain.

If the CPU enters a sleep mode that disables clocks used by the TWIM, the TWIM will stop func-
tioning and resume operation after the system wakes up from sleep mode.

TWI 

Master

TWD

TWCK

Atmel TWI

serial EEPROM

I

2

C RTC

I

2

C LCD

controller

I

2

C temp

sensor

Slave  2

Slave  3

Slave  4

VDD

Rp: pull-up value as given by the I2C Standard

Slave 1

Rp

Rp

I/O Lines Description

TWD

Two-wire Serial Data

Input/Output

TWCK

Two-wire Serial Clock

Input/Output