9

AT91SAM7A2 - Summary

6021AS–ATARM–03/04

•

Automatic Reply After Receive a Remote Frame

•

Time Stamp on Each Transfer

•

Multicast Reception with Time Synchronization

•

Continuous Reception Mode

GPT: General

Purpose Timer

The AT91SAM7A2 features four General Purpose Timers. Each timer can be independently

programmed to perform a wide range of functions including frequency measurement, event

counting, interval measurement, pulse generation, delay timing and pulse width modulation.

Each General Purpose Timer has one external clock input, five internal clock inputs, and three

multi-purpose input/output signals which can be configured by the user. Each timer drives an

internal interrupt signal which can be programmed to generate processor interrupts via the

AIC (Advanced Interrupt Controller).

Three General Purpose Timers are grouped in the same block. This block has two global reg-

isters which act upon all three GPTs. The Block Control Register allows the three timers to be

started simultaneously with the same instruction. The Block Mode Register defines the exter-

nal clock inputs for each timer, allowing them to be chained.

ST: Simple Timer

Simple Timers provide basic functions for timing calculation. Each channel of this timer has a

specific prescalar and a 16-bit counter. The prescalar defines the clock frequency of the chan-

nel counter. The 16-bit counter starts down-counting when a value different than zero is

loaded. An interrupt is generated when the counter is null.

CAPT: Capture

Module

The capture module is a frame analyzer. It stores the period of time between two edges of a

signal in a register. This period is described as a number of counter cycles. The capture allows

data transfers with the PDC.

PWM: Pulse Width

Modulation

The AT91SAM7A2 includes four PWM channels. Each channel can generate pulses. The fre-

quency and the duty cycle of each channel can be configured.

WT: Watch Timer

The watch timer provides a seconds counter and an alarm function. The alarm register has a

resolution of 30.5 µs. This allows a 32-bit register to have sufficient range to cater for a 24 or

36 hour period.

WD: Watch Dog

The AT91SAM7A2 has an internal watchdog which can be used to prevent system lock-up if

the software becomes trapped in a deadlock.

SFM: Special

Function Module

The AT91SAM7A2 provides registers which implement the following special functions.

•

Chip Identification

•

RESET Status