STMicroelectronics STM32F042C4, Manual

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STM32F042xx Electrical characteristics
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6.3.7 External clock source characteristics
High-speed external user clock generated from an external source
In bypass mode the HSE oscillator is switched off and the input pin is a standard GPIO.
The external clock signal has to respect the I/O characteristics in Section 6.3.14 . However,
the recommended clock input waveform is shown in Figure 15: High-speed external clock
source AC timing diagram .
Figure 15. High-speed external clock source AC timing diagram
Table 34. High-speed external user clock characteristics
Symbol Parameter
(1)
Conditions Min Typ Max Unit
f
HSE_ext
User external clock source frequency - - 8 32 MHz
V
HSEH
OSC_IN input pin high level voltage - 0.7 V
DDIOx
- V
DDIOx
V
V
HSEL
OSC_IN input pin low level voltage - V
SS
- 0.3 V
DDIOx
t
w(HSEH)
t
w(HSEL)
OSC_IN high or low time - 15 - -
ns
t
r(HSE)
t
f(HSE)
OSC_IN rise or fall time - - - 20
1. Guaranteed by design, not tested in production.
069
9+6(+
WI+6(
7+6(
W
WU+6(
9+6(/
WZ+6(+
WZ+6(/