Cypress FR81S CY91F52 Series Recommendation For Hardware Setup page 21

By closing the switch SW at time t
But at the port pin Pxy on point (B) the following voltage can be measured:
By closing the switch SW the circuit becomes a parallel oscillator with the wire-inductivity LX, the debouncing capacity
C and the damping RPD of the pull-down resistor (Assume the power supply to be ideal, i.e. it has no internal
X
resistance):
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the following voltage can be measured at point (A):
0
Figure 22. Signal rise on switch closing (Point A)
Figure 23. Signal rise on switch closing (Point B)
Figure 24. Equivalent circuit on switch closed
Document No. 002-09375 Rev. *B
Recommendation for Hardware Setup 32-Bit FR81S Family
21