Case 1: Three-Sample Sampling Window Width; Case 2: Six-Sample Sampling Window Width - Texas Instruments Concerto F28M36 Series Technical Reference Manual

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Example: Minimum Sampling Frequency:
If GPxCTRL[QUALPRDn] = 0xFF (i.e. 255)
then the sampling frequency is f
If, for example, f
then the signal will be sampled at 150 MHz × 1 ÷ (2 × 255) or one sample every 3.4 μs.
Number of samples:
The number of times the signal is sampled is either three samples or six samples as specified in the
qualification selection (GPxQSEL1 and GPxQSEL2, registers). When three or six consecutive cycles are
the same, then the input change will be passed through to the DSP.
Total Sampling Window Width:
The sampling window is the time during which the input signal will be sampled as shown in
By using the equation for the sampling period along with the number of samples to be taken, the total
width of the window can be determined.
For the input qualifier to detect a change in the input, the level of the signal must be stable for the duration
of the sampling window width or longer.
The number of sampling periods within the window is always one less then the number of samples taken.
For a thee-sample window, the sampling window width is 2 sampling periods wide where the sampling
period is defined in
sampling periods wide.
the total sampling window width based on GPxCTRL[QUALPRDn] and the number of samples taken.
If GPxCTRL[QUALPRDn] = 0
If GPxCTRL[QUALPRDn] ≠ 0
If GPxCTRL[QUALPRDn] = 0
If GPxCTRL[QUALPRDn] ≠ 0
NOTE: The external signal change is asynchronous with respect to both the sampling period and
SYSCLKOUT. Due to the asynchronous nature of the external signal, the input should be
held stable for a time greater than the sampling window width to make sure the logic detects
a change in the signal. The extra time required can be up to an additional sampling period +
T
SYSCLKOUT
The required duration for an input signal to be stable for the qualification logic to detect a
change is described in the device specific data manual.
Example Qualification Window:
For the example shown in
• GPxQSEL1/2 = 1,0. This indicates a six-sample qualification.
• GPxCTRL[QUALPRDn] = 1. The sampling period is t
This configuration results in the following:
• The width of the sampling window is: .
SPRUHE8E – October 2012 – Revised November 2019
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× 1 ÷ (2 × GPxCTRL[QUALPRDn])
SYSCLKOUT
= 150 MHz
SYSCLKOUT
Table 4-39. Likewise, for a six-sample window, the sampling window width is 5
Table 4-41 and Table 4-42
Table 4-41. Case 1: Three-Sample Sampling Window Width
Total Sampling Window Width
2 × T
SYSCLKOUT
2 × 2 × GPxCTRL[QUALPRDn] × T
Where T
Table 4-42. Case 2: Six-Sample Sampling Window Width
Total Sampling Window Width
5 × T
SYSCLKOUT
5 × 2 × GPxCTRL[QUALPRDn] × T
Where T
.
Figure 4-41, the input qualification has been configured as follows:
Copyright © 2012–2019, Texas Instruments Incorporated
C28 General-Purpose Input/Output (GPIO)
show the calculations that can be used to determine
SYSCLKOUT
is the period in time of SYSCLKOUT
SYSCLKOUT
SYSCLKOUT
is the period in time of SYSCLKOUT
SYSCLKOUT
(SP) = 2 × GPxCTRL[QUALPRDn] × T
w
General-Purpose Input/Output (GPIO)
Figure 4-41.
.
SYSCLKOUT
391