Datasheet

DS12167 Rev 4 23/94
STM8L050J3 Functional overview
43
Recommendations for SWIM pin (pin#1) sharing
If the SWIM pin should be used with the I/O pin functionality, it is recommended to add a ~5
seconds delay in the firmware before changing the functionality on the pin with SWIM
functions. This action allows the user to set the device into SWIM mode after the device
power on and to be able to reprogram the device. If the pin with SWIM functionality is set to
I/O mode immediately after the device reset, the device is unable to connect through the
SWIM interface and it will be locked forever (if the NRST pin is not available on the
package). This initial delay can be removed in the final (locked) code.
If the initial delay is not acceptable for the application there is the option that the firmware
reenables the SWIM pin functionality under specific conditions such as during firmware
startup or during application run. Once that this procedure is done, the SWIM interface can
be used for device debug/programming.
Bootloader
STM8L050J3 features a built-in bootloader(which supports USART interface on pins 8 and
1: PC5
= TxD, PC6 RxD). See STM8 bootloader user manual (UM0560).
The bootloader is used to download application software into the device memories,
including RAM, program and data memory, using standard serial interfaces. It is a
complementary solution to programming via the SWIM debugging interface.
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