Datasheet

446
32072H–AVR32–10/2012
AT32UC3A3
22.5 Application Block Diagram
Figure 22-2. Application Block Diagram
22.6 I/O Lines Description
22.7 Product Dependencies
In order to use this module, other parts of the system must be configured correctly, as described
below.
22.7.1 I/O Lines
TWDand TWCK are bidirectional lines, connected to a positive supply voltage via a current
source or pull-up resistor (see Figure 22-5 on page 448). 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.
TWALM, 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, TWCK, and optionally TWALM as peripheral lines.
– Define TWD, TWCK, and optionally TWALM as open-drain.
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
Table 22-4. I/O Lines Description
Pin Name Pin Description Type
TWD Two-wire Serial Data Input/Output
TWCK Two-wire Serial Clock Input/Output
TWALM SMBus SMBALERT Input/Output