TMS320F28027_14 Datasheet, PDF (96/132 Pages) Texas Instruments – Piccolo™ Microcontrollers

TMS320F28027, TMS320F28026, TMS320F28023, TMS320F28022
TMS320F28021, TMS320F28020, TMS320F280200
SPRS523J – NOVEMBER 2008 – REVISED OCTOBER 2013
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6.10.3 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
SYSCLK
GPIOxn
t_w(GPI)
Figure 6-12. General-Purpose Input Timing
V_DDIO
> 1 MS
2 pF
V_SS
V_SS
Figure 6-13. Input Resistance Model for a GPIO Pin With an Internal Pull-up
96
Electrical Specifications
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