Figure 22. Hse32 Clock Sources - STMicroelectronics STM32WLEx Reference Manual

Reset and clock control (RCC)
External crystal (HSE32 crystal)
The associated hardware configuration is shown in
to the electrical characteristics section of the datasheet for more details.
Frequency trimming
When using HSE32 with external crystal, the load capacitors are provided by the integrated
capacitor banks, that can be trimmed. The HSE32 load capacitor trimming allows a
compensation of device manufacturing process variations, used crystal and PCB design.
The HSE32 frequency can be tuned in the application via the sub-GHz radio registers
SUBGHZ_HSEINTRIMR and SUBGHZ_HSEOUTRIMR. For more information see
Section 4.4: Sub-GHz radio
The HSE32 frequency can be measured by outputting the HSE32 clock on the MCO when
in Run mode.
External source (HSE32 TXCO)
In this mode, an external TXCO clock source must be provided. This external source
frequency must be 32 MHz. This mode is selected by setting the HSEBYPPWR and
HSEON bits in the
the datasheet) must drive the following pins (see
•
OSC_IN and OSC_OUT pins: OSC_IN pin must be driven, while the OSC_OUT pin
must be left not connected.
The TCXO supply can be provided by the device on PB0/VDDTCXO. The V
is also enabled with the HSEBYPPWR bit in
enabling the HSE32 oscillator. V
be configured through the sub-GHz radio Set_TcxoMode() command (see
Sub-GHz radio (SUBGHZ)
236/1306

Figure 22. HSE32 clock sources

Clock source
C
Crystal
OSC_IN
OSC_IN
External
VDDTCXO
TCXO C
TCXO
clocks.
RCC clock control register
DDTCXO
for more details).
RM0461 Rev 5
Hardware configuration
tunable load
capacitors
LIN
OSC_OUT
OSC_OUT
Not
connected
External
clock source
C
LIN
OSC_IN OSC_OUT
C
Not connected
Note: Force SUBGHZ_HSEINTRIMR = 0x00
R
to get C = 11.3 pF.
LIN
Figure 22: HSE32 clock
(RCC_CR). The external clock signal (refer to
Figure 22: HSE32 clock
RCC clock control register (RCC_CR)
supply level and TCXO clock startup timeout can
RM0461
C
LOUT
MSv62606V2
sources. Refer
sources):
supply
DDTCXO
before
Section 4: