Datasheet

280
6120F–ATARM–03-Oct-06
AT91SAM7X512/256/128 Preliminary
29.4 Product Dependencies
29.4.1 I/O Lines Description
29.4.2 I/O Lines
Both TWD and TWCK are bi-directional lines, connected to a positive supply voltage via a cur-
rent source or pull-up resistor (see Figure 29-2 on page 279). 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 steps:
• Program the PIO controller to:
– Dedicate TWD and TWCK as peripheral lines.
– Define TWD and TWCK as open-drain.
29.4.3 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.
29.4.4 Interrupt
The TWI interface has an interrupt line connected to the Advanced Interrupt Controller (AIC). In
order to handle interrupts, the AIC must be programmed before configuring the TWI.
Table 29-1. I/O Lines Description
Pin Name Pin Description Type
TWD Two-wire Serial Data Input/Output
TWCK Two-wire Serial Clock Input/Output