STMicroelectronics STM32 Cortex-M3, Руководство пользователя

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1 Intro
2 Electrocardiogram ( Ecg ) Signals
The Electrocardiogram (
Ecg
)
•
Ecg
: electrical manifestation of heart activity recorded
from the body surface
•
monitoring of heart rate
The
Ecg
signal can be recorded fairly easily with surface
electrodes placed on the limbs and/or the chest, see pages 6 – 16
below.
Josef Goette 2 2009
4 Peripherals
4.7 System Timer (SysTick)
b
sysTick
F sets up a system timer routine and shows a running light on GPIOB. The system
timer is a periodical timer that can be set up easily with the configuration wizard
(see Figure
4.8 ).
The Cortex core includes a 24-bit down counter, with auto reload and end of count interrupt. This
is intended to provide a standard timer for all Cortex-based microcontrollers. The SysTick timer
is intended to be used to provide a system tick for an RTOS, or to generate a periodic interrupt for
scheduled tasks. The SysTick Control and status register in the Cortex-M3 System control space
unit allows you to select the SysTick clock source. By setting the CLKSOURCE bit the SysTick
timer will run at the CPU frequency. When cleared the timer will run at 1/8 CPU frequency.
4.7.1 Configuration
Enable the System Timer Configuration in the configuration wizard and select a clock source. Choose
the time interval and enable the interrupt. The function
void SysTick Handler (void)
above
the
main()
-routine gets called when the sysTick interrupt occurs.
Figure 4.8: System Timer Configuration Wizard
32 STM32 Cortex-M3 Tutorial