Appendix B: GPIO Control
•
75
in the accompanying diagrams, the delay is the time between the trigger and the pulse
transitions. The width is the time the pulse stays at the active level before transitioning. The
periodic mode, the delay determines the low time of the pulse.
Each pulse generator generates a signal that can be used as an input to the GPIO Control
Block. A triggered pulse generator needs an input signal that comes from an output of the
GPIO Control Block.
Note:
There is one clock cycle between the output signal of a pulse generator and the outputs
of the GPIO Control Block.
The labels for the inputs from the pulse generators in the GPIO Control Block programming
languages are:
•
I7, for pulse generator 0
•
I6, for pulse generator 1
Rescaler
The Rescaler lets you change the frequency of a periodic input signal. You can use the
Rescaler to multiply the period by up to 4096 or divide it by up to 4095.
Figure 57: Granularity
The Rescaler is defined by the following settings:
Granularity
The granularity is the number of clock cycles during which the rescaler checks for activity on
its input. The value to use depends on the period/frequency of the input signal. If a
frequency lies between two different granularity settings, the lowest setting will yield a
better precision. The possible values are:
Acceptable Line rate relative to Granularity
Gran
Precision
Minimum
Period
Maximum Period
Min.
Frequency
Max. Freq.
(ER<1%)
(30 ns)
(s)
(s)
(Hz)
(Hz)
0
1
0.00000006
0.00197
509
333,333
