User manual

PSMC Designer User’s Guide
DS40001671B-page 16  2012-2013 Microchip Technology Inc.
FIGURE 2-4: BLANKING CONTROL
All asynchronous inputs pass through blanking. Rising and falling events are used as
the blanking triggers because these are the two events that signal the output power
drivers to turn on and off. When a power driver switches it can cause spurious
transients in the system that can cause false event triggers if not suppressed. A
blanked input is suppressed for all of the following:
• Period event
• Rising event
• Falling event
• Shutdown event
Modulation sources are the only inputs that are not affected by blanking.
Note that, in Figure 2-4, the signal names entering the blanking control on the left are
the same names, but appended by a “_B” when leaving on the right. You will notice that
the input signal identifiers in the other GUIs are also appended with a “_B”, as a
reminder that those inputs pass through the blanking function and may be blanked.
2.14.1 Blanking Times
The blanking time is entered in the appropriate text box in microseconds. The blanking
count value is calculated from the entered time based on the psmc_clk frequency. If
the calculated count value exceeds the maximum allowed then a warning dialog will
appear indicating the limit. If the psmc_clk frequency is changed then a new time
based on the new frequency and existing count will be displayed in the text box.
2.14.2 Rising Event Trigger
Click on the switch at the blanking time output to enable or disable the rising event
blanking trigger. Asynchronous inputs are selected for rising event blanking individually
by closing the switch to the AND gate output in their path.