ST UM1472, User Manual

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Hardware and layout STM32F4DISCOVERY
18/38 Doc ID 022256 Rev 2
4.10 OSC clock
4.10.1 OSC clock supply
If PH0 and PH1 are only used as GPIOs instead of as a clock, then SB13 and SB14 are
closed and R24, R25 and R68 are removed.
●
MCO from ST-LINK
. From MCO of the STM32F103. This frequency cannot be
changed, it is fixed at 8 MHz and connected to PH0-OSC_IN of the STM32F407VGT6.
Configuration needed:
–
SB13, SB14 OPEN
– R25
(a)
removed
– R68
(a)
soldered
●
Oscillator onboard
. From X2 crystal. For typical frequencies and its capacitors and
resistors, please refer to the STM32F407VGT6 Datasheet. Configuration needed:
–
SB13, SB14 OPEN
– R25
(a)
soldered
– R68
(a)
removed
●
Oscillator from external PH0
. From external oscillator through pin 7 of the P2
connector. Configuration needed:
–
SB13 closed
– SB14 closed
– R25 and R68 removed
4.10.2 OSC 32 KHz clock supply
If PC14 and PC15 are only used as GPIOs instead of as a clock, then SB15 and SB16 are
closed, and R21 and R22 are removed.
●
Oscillator onboard . From X1 Crystal (not provided). Configuration needed:
– SB15, SB16 OPEN
– C16, C27, R21 and R22 soldered.
●
Oscillator from external PC14
. From external oscillator trough the pin 9 of P2
connector. Configuration needed:
–
SB16 closed
– SB15 closed
– R21 and R22 removed
a. As the frequency supplied by X2 is the same as MCO (8 MHz) R25 and R68 are soldered.