1.4.4.3 Qualification Using a Sampling Window
In this mode, the signal is first synchronized to the system clock (SYSCLKOUT) and then qualified by a specified
number of cycles before the input is allowed to change.
show how the input
qualification is performed to eliminate unwanted noise. Two parameters are specified by the user for this type
of qualification: 1) the sampling period, or how often the signal is sampled, and 2) the number of samples to be
taken.
GPxCTRL Reg
SYNC
SYSCLKOUT
Qualification
Input Signal
Qualified By 3
or 6 Samples
GPIOx
Time between samples
GPxQSEL1/2
Number of Samples
Figure 1-63. Input Qualification Using a Sampling Window
Time between samples (sampling period):
To qualify the signal, the input signal is sampled at a regular period. The sampling period is specified by the user
and determines the time duration between samples, or how often the signal will be sampled, relative to the CPU
clock (SYSCLKOUT).
The sampling period is specified by the qualification period (QUALPRDn) bits in the GPxCTRL register.
The sampling period is configurable in groups of 8 input signals. For example, GPIO0 to GPIO7 use
GPACTRL[QUALPRD0] setting and GPIO8 to GPIO15 use GPACTRL[QUALPRD1].
and
show the relationship between the sampling period or sampling frequency and the GPxCTRL[QUALPRDn]
setting.
Table 1-59. Sampling Period
Sampling Period
If GPxCTRL[QUALPRDn] = 0
1 × T
SYSCLKOUT
If GPxCTRL[QUALPRDn] ≠ 0
2 × GPxCTRL[QUALPRDn] × T
SYSCLKOUT
Where T
SYSCLKOUT
is the period in time of SYSCLKOUT
Table 1-60. Sampling Frequency
Sampling Frequency
If GPxCTRL[QUALPRDn] = 0
f
SYSCLKOUT
If GPxCTRL[QUALPRDn] ≠ 0
f
SYSCLKOUT
× 1 ÷ (2 × GPxCTRL[QUALPRDn])
Where f
SYSCLKOUT
is the frequency of SYSCLKOUT
System Control and Interrupts
SPRUH18I – JANUARY 2011 – REVISED JUNE 2022
TMS320x2806x Microcontrollers
117
Copyright © 2022 Texas Instruments Incorporated
Содержание TMS320 2806 Series
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