Datasheet

687
SAM4S Series [DATASHEET]
11100F–ATARM–29-Jan-14
34.5 Application Block Diagram
Figure 34-2. Application Block Diagram
34.5.1 I/O Lines Description
34.6 Product Dependencies
34.6.1 I/O Lines
Both TWD and TWCK are bidirectional lines, connected to a positive supply voltage via a current source or pull-up
resistor (see Figure 34-2). 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-collector to perform the wired-AND function.
TWD and TWCK pins may be multiplexed with PIO lines. To enable the TWI, the programmer must perform the following
step:
 Program the PIO controller to dedicate TWD and TWCK as peripheral lines.
The user must not program TWD and TWCK as open-drain. It is already done by the hardware.
34.6.2 Power Management
The TWI interface may be clocked through the Power Management Controller (PMC), thus the programmer must first
configure the PMC to enable the TWI clock.
Host with
TWI
Interface
TWD
TWCK
Atmel TWI
Serial EEPROM
I²C RTC
I²C LCD
Controller
Slave 1 Slave 2 Slave 3
V
DD
I²C Temp.
Sensor
Slave 4
Rp: Pull-up value as given by the I²C Standard
Rp Rp
Table 34-3. I/O Lines Description
Pin Name Pin Description Type
TWD Two-wire Serial Data Input/Output
TWCK Two-wire Serial Clock Input/Output
Table 34-4. I/O Lines
Instance Signal I/O Line Peripheral
TWI0 TWCK0 PA4 A
TWI0 TWD0 PA3 A
TWI1 TWCK1 PB5 A
TWI1 TWD1 PB4 A