at91rm3400 ATMEL Corporation, at91rm3400 Datasheet - Page 155

• Manufacturer Part Number: at91rm3400
• Description: Atmel Advanced At91 Arm Microcontroller
• Manufacturer: ATMEL Corporation

System Timer (ST)
Overview
Block Diagram
Application
Block Diagram
1790A–ATARM–11/03
The System Timer (ST) module integrates three different free-running timers:
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These timers count using the Slow Clock provided by the Power Management Controller. Typ-
ically, this clock has a frequency of 32.768 kHz, but the System Timer might be configured to
support another frequency.
The System Timer provides an interrupt line connected to one of the sources of the Advanced
Interrupt Controller (AIC). Interrupt handling requires programming the AIC before configuring
the System Timer. Usually, the System Timer interrupt line is connected to the first interrupt
source line and shares this entry with the Debug Unit (DBGU) and the Real Time Clock (RTC).
This sharing requires the programmer to determine the source of the interrupt when the
source 1 is triggered.
Important features of the System Timer include:
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Figure 47. System Timer Block Diagram
Figure 48. Application Block Diagram
A Period Interval Timer (PIT) that sets the time base for an operating system.
A Watchdog Timer (WDT) with system reset capabilities in case of software deadlock.
A Real-Time Timer (RTT) counting elapsed seconds.
One Period Interval Timer, 16-bit Programmable Counter
One Watchdog Timer, 16-bit Programmable Counter
One Real-time Timer, 20-bit Free-running Counter
Interrupt Generation on Event
Management
Controller
Power
OS or RTOS
Scheduler
PIT
APB
SLCK
Advanced Interrupt Controller
Date, Time
and Alarm
Periodic Interval Timer
Manager
RTT
System Timer
Real-Time Timer
Watchdog Timer
STIRQ
System Survey
Manager
WDT
AT91RM3400
NWDOVF
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