DC Operating Frequency of Microcontroller

[dilshan]

While referring some datasheets (e.g: PIC16F73) I found that "Operating Frequency" of a Microcontroller is "DC-20MHz". What is the meaning of "DC" part of the operating frequency?

Is it possible to have DC component in frequency?

 

[tpetar]

Constant electrical current (which would be the case where a constant electrical voltage flows in a single direction within an electrical circuit with a unvarying electrical load resistance), or it can be constantly varying as the result of changes in supply voltage and/or electrical circuit resistance changes and/or electrical circuit load changes. It is still Direct Current as long as the electrical current flow is in a single direction. Such current can vary in an infinite number of ways and still be DC as long as current flow in held to a single direction within the electrical circuit.



https://en.wikipedia.org/wiki/Direct_current

 

[dilshan]

Thanks tpetar !

 

[RetroTechie]

In the context of "Microcontroller operating frequency = DC-20 MHz", DC should simply be read as "0 Hz".

Read: another way of saying "microcontroller clock can be stopped entirely, clock period can be stretched indefinitely". That is a property which doesn't hold for all microcontrollers / CPU's, so where it does it's worth reporting. Useful for debugging purposes (single-stepping the clock signal & checking out results), and when in order to conserve power, you want the lowest possible clock frequency that still lets the controller do its job.

 

[keith1200rs]

The reason for the data sheet saying DC in the clock specification is to make it clear that the microcontroller uses static logic, not dynamic. In other words, you can clock it as slow as you like, and even stop and start the clock.

Some digital logic is dynamic, e.g. Dynamic RAM and cannot be clocked below a certain frequency otherwise it will not function correctly.

Keith