Case 1: Three-Sample Sampling Window Width; Case 2: Six-Sample Sampling Window Width - Texas Instruments Concerto F28M35 Series Technical Reference Manual

C28 General-Purpose Input/Output (GPIO)
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: .
t (IQSW) = 5 × t
w
• If, for example, T
t (IQSW) = 5 × 2 × 6.67 ns =66.7 ns.
w
• To account for the asynchronous nature of the input relative to the sampling period and SYSCLKOUT,
up to an additional sampling period, t
input signal. For this example:
t (SP) + T
w SYSCLKOUT
• In Figure 4-41, the glitch (A) is shorter then the qualification window and will be ignored by the input
qualifier.
382
General-Purpose Input/Output (GPIO)
Table 4-42. Case 1: Three-Sample Sampling Window Width
Total Sampling Window Width
2 × T
SYSCLKOUT
2 × 2 × GPxCTRL[QUALPRDn] × T
Where T
Table 4-43. 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:
(SP) = 5 × 2 × GPxCTRL[QUALPRDn] × T
w
= 6.67 ns, then the duration of the sampling window is:
SYSCLKOUT
(SP), + T
w
= 333.4 ns + 66.67 ns = 400.1 ns
Copyright © 2012–2019, Texas Instruments Incorporated
SYSCLKOUT
is the period in time of SYSCLKOUT
SYSCLKOUT
SYSCLKOUT
is the period in time of SYSCLKOUT
SYSCLKOUT
(SP) = 2 × GPxCTRL[QUALPRDn] × T
w
SYSCLKOUT
may be required to detect a change in the
SYSCLKOUT
SPRUH22I – April 2012 – Revised November 2019
www.ti.com
SYSCLKOUT
or 5 × 2 × T
SYSCLKOUT
Submit Documentation Feedback
.