Atmel Xplained Evaluation Board AT32UC3A3-XPLD AT32UC3A3-XPLD Data Sheet

32072H–AVR32–10/2012

Figure 23-2. 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.

TWALM is used to implement the optional SMBus SMBALERT signal.

The TWALM, 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, and optionally TWALM as peripheral lines.

– Define TWD, TWCK, and optionally TWALM 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

TWALM

Slave 1

Rp

Rp

Rp

I/O Lines Description

TWD

Two-wire Serial Data

Input/Output

TWCK

Two-wire Serial Clock

Input/Output

TWALM

SMBus SMBALERT

Input/Output