6.7.2 OSC clock supply
There are four ways to configure the pins corresponding to the high‑speed external clock (HSE):
HSE: On-board oscillator X1 crystal (default configuration)
For typical frequencies, capacitors, and resistors, refer to the STM32 microcontroller datasheet. Refer to the
application note
Oscillator design guide for STM8AF/AL/S, STM32 MCUs and MPUs (AN2867). The X1 crystal
has the following characteristics: 24 MHz, 6 pF, and 20 ppm. It is recommended to use NX2016SA-24MHz-
EXS00A-CS10820 manufactured by NDK. The following configuration is needed:
• SB14 and SB15 ON are connected to the external HSE.
• SB16 (MCO) OFF
• SB66 and SB67 OFF. The ST morpho pins are disconnected.
MCO from STLINK-V3EC
The MCO output of the STLINK-V3EC MCU is used as an input clock. This frequency cannot be changed. It is
fixed at 8 MHz, and connected to PH0 OSC_IN of the STM32 microcontroller. The following configuration is
needed:
• SB16 ON. MCO is connected to PH0 and R62 on the STLINK-V3EC side and must be connected to
provide the MCO to the
STLINK-V3EC output.
• SB14 and SB15 OFF. The external crystal is not connected to HSE.
• SB66 and SB67 OFF. The ST morpho pins are disconnected.
External oscillator
The input clock comes from an external oscillator through PH0, CN11 pin 29. The following configuration is
needed:
• SB66 ON. The ST morpho connector is connected to PH0.
• SB16 OFF. MCO is not connected to PH0.
• SB14 and SB15 OFF. The external crystal is not connected to HSE.
HSE not used
PH0 and PH1 are used as GPIOs instead of clocks. The following configuration is needed:
• SB16 OFF. MCO is not connected to PH0.
• SB14 and SB15 OFF. The external crystal is not connected to HSE.
• SB66 and SB67 ON. The ST morpho pins are connected as GPIOs.
6.8
Reset sources
The reset signal of the Nucleo board is active LOW and the reset sources include:
• The RESET button (B1)
• The embedded STLINK-V3EC
• The ARDUINO
®
‑included Zio connector (CN8) pin 5
• The ST morpho connector (CN11) pin 14
6.9
Virtual COM port
The serial interface UART3 (PD8/PD9) that supports the bootloader is directly available as a Virtual COM port of
the PC connected to the STLINK-V3EC USB connector (CN5). The VCP configuration is the following:
• 115200 bps
• 8-bit data
• No parity
• One-stop bit
• No flow control
UM3276
Hardware layout and configuration
UM3276 - Rev 1
page 22/40
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