Datasheet

466
11011B–ATARM–21-Feb-12
SAM3N
466
11011B–ATARM–21-Feb-12
SAM3N
28.6 Product Dependencies
28.6.1 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 28-2 on page 465). 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 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.
28.6.2 Power Management
• Enable the peripheral clock.
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.
28.6.3 Interrupt
The TWI interface has an interrupt line connected to the Nested Vector Interrupt Controller
(NVIC). In order to handle interrupts, the NVIC must be programmed before configuring the TWI.
Table 28-4. 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
Table 28-5. Peripheral IDs
Instance ID
TWI0 19
TWI1 20