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SPRS439I – JUNE 2007 – REVISED MARCH 2011
6.9.3
Sampling Window Width for Input Signals
The following section summarizes the sampling window width for input signals for various input qualifier
configurations.
Sampling frequency denotes how often a signal is sampled with respect to SYSCLKOUT.
Sampling frequency = SYSCLKOUT/(2 * QUALPRD), if QUALPRD
≠
0
Sampling frequency = SYSCLKOUT, if QUALPRD = 0
Sampling period = SYSCLKOUT cycle x 2 x QUALPRD, if QUALPRD
≠
0
In the above equations, SYSCLKOUT cycle indicates the time period of SYSCLKOUT.
Sampling period = SYSCLKOUT cycle, if QUALPRD = 0
In a given sampling window, either 3 or 6 samples of the input signal are taken to determine the validity of
the signal. This is determined by the value written to GPxQSELn register.
Case 1:
Qualification using 3 samples
Sampling window width = (SYSCLKOUT cycle x 2 x QUALPRD) x 2, if QUALPRD
≠
0
Sampling window width = (SYSCLKOUT cycle) x 2, if QUALPRD = 0
Case 2:
Qualification using 6 samples
Sampling window width = (SYSCLKOUT cycle x 2 x QUALPRD) x 5, if QUALPRD
≠
0
Sampling window width = (SYSCLKOUT cycle) x 5, if QUALPRD = 0
XCLKOUT
GPIOxn
t
w(GPI)
Figure 6-11. General-Purpose Input Timing
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Electrical Specifications
133
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