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Example 3: Manual clock switching

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Example 3: Manual clock switching

3.1

Overview

This example demonstrates how to manually switch the STM8A master clock from one clock

source to another. Manual switching requires more instructions than automatic switching

(described in Section 2) but it gives the application precise control of the switch event time.

This example is provided as CLK example 3 in the STM8 firmware library.

3.2

Hardware description

The STM8/128-EVAL evaluation board is used for this example. The main hardware

connections are shown in Figure 1.

3.3

Firmware description

When this example is running on the evaluation board, the user can select a new clock

source using the joystick (see Table 1).

Each time a clock source is selected, LEDs 1 to 3 blink for a short period. Clock switching

can also be monitored by connecting an oscilloscope to the CCO pin (PE0 ).