Software description

AN3265

10/19

Doc ID 17860 Rev 1

2.1.4

CLK

The clock control enables and delivers the correct clock frequency to the CPU and

peripherals. It configures the HSI and HSE prescalers division factor from 8 to 1.

2.1.5

GPIOs

The application drives the MCU I/Os to interface the microcontroller with external hardware

components, i.e. the LEDs and the pushbuttons.

2.1.6

EXTI

The external interrupt sensitivity is configured to trigger an interrupt each time a falling edge,

and only a falling edge, is detected on PB0.

2.1.7

Data EEPROM

The SystemState variable represents the current state of the application. It is stored in the

STM8S105C6T6 data EEPROM thus allowing to save the application progress in the state

machine when the microcontroller is reset (see Figure 5).

2.1.8

RST

The reset register (RST_SR) is used in conjunction with the IWDG and WWDG to determine

which of them has triggered a reset.

2.1.9

CCO

The Configurable clock output register (CLK_CCOR) allows to select the clock source that is

output on the CCO pin.

2.2

Exclusion of the Standard STM8S standard firmware library

As this application uses optimized code, the stm8s.h file must be modified not to include the

STM8S standard firmware library. This is done by commenting the following define

statement:

#define USE_STDPERIPH_DRIVER