General
Review and verify the following for the custom
schematic design:
- Reviewed above "Common
checklist for all sections" section of the user's guide.
- Configuration of CLKOUT0 and
WKUP_CLKOUT0 clock outputs.
Schematic Review
Follow the list below for the custom
schematic design:
- WKUP_CLKOUT0 is driven low
after reset. Add a TP for testing.
- When the WKUP_CLKOUT0 is used
as an IO or as a 32.768kHz clock source, custom board designer is expected
to consider the effect of the output being 25MHz being the output during the
reset.
- Series resistor 0Ω provision is provided to control possible signal
reflection.
- Connection of clock output to single or multiple loads. When connected to
multiple loads (inputs), each of attached device inputs are recommended to
be connected to a buffered output.
- Pulls are provided near to the attached device clock input that can float
(to prevent the attached device inputs from floating until host software
configures the clock output).
Additional
- EXT_REFCLK1 can be configured as CLKOUT0. The recommendation is to connect clock
signal as point-to-point, without any branches. When connecting CLKOUT0 to
multiple clock inputs, use a buffer (with one input and multiple outputs or
individual buffers (based on the application use case)).
- The CLKOUT0 and WKUP_CLKOUT0 clock outputs performance is not defined in the
processor-specific data sheet since there are a number of boards or end
equipment specific dependencies that can impact the clock performance.