Texas Instruments TMS320F2802 - Manual (Page 111)

GPIOxn
XCLKOUT
t
w(GPI)
TMS320F2809, TMS320F2808, TMS320F2806
TMS320F2802, TMS320F2801, TMS320C2802
TMS320C2801, TMS320F28016, TMS320F28015
www.ti.com SPRS230N – OCTOBER 2003 – REVISED MAY 2012
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
Figure 6-13. General-Purpose Input Timing
NOTE
The pulse-width requirement for general-purpose input is applicable for the XINT2_ADCSOC
signal as well.
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