Design Aids - Filters Clock

Questa mi sembra una considerazione abbastanza importante per cominciare a capire come funziona:

One of the important things to note about designing a filter is that the cutoff frequency
of the filter is based on the clock frequency being sent to the analog columns
that contain the filter. The filter design wizard does not set up resources to generate
this frequency for you. It simply tells you what frequency is important. The specified
frequency must be sent to all switched cap blocks used in the filter. You will be
required to create a clock using digital resources to send to the analog column. This
clock can come from timers, counters, and so on. If the clock is attainable by using
the VC1, VC2, or VC3 (or 24V1, 24V2) signals, you can reserve your digital blocks
for other uses.
Since there are limits on what clocking frequencies can be set to the blocks, there
are limits on what frequencies you are able to choose for your filters. That is the
reason why you won’t find a high-pass filter design in the PSoC. Unfortunately, this
is the nature of switched capacitor designs. If filters that exceed these capabilities are
needed in your designs, then the filter must be handled by external circuitry.

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