AT91SAM7XC256 Datasheet, PDF (278/675 Pages) ATMEL Corporation – Thumb-based Microcontrollers

30.4 Product Dependencies
30.4.1 I/O Lines Description
Table 30-1.
Pin Name
TWD
TWCK
I/O Lines Description
Pin Description
Two-wire Serial Data
Two-wire Serial Clock
Type
Input/Output
Input/Output
30.4.2 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 30-2 on page 277). 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.
30.4.3
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.
30.4.4 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.
278 AT91SAM7XC256/128 Preliminary
6209B–ATARM–10-Feb-06