Measuring Periods w/ Motorola HS12 ICs

[formulajoe]

I was designing a circuit to determine frequency of signals using a counter as the main part of the circuit. However, I was just informed that period must also be measured or have the circuit perform one of the other.
Are there ICs that are able to determine the period between rising edges? If so, I will be able to use transistors to multiplex between frequency or period measurement.
The microcontroller I will be using is the motorola HS12. I know there are some ports on the HS12 that can be used for input-capture. The period could easily be found using these ports. Can these ports also be configured for pulse accumulation?

 

[berkeman]

If you want to turn a frequency meter into a period measuring device, just put a known clock into the input of the frequency meter, and trigger the meter with your signal that you want the period of. Put in 1MHz into the frequency counter's input if you want the period readout in microseconds.

I'm not familiar with the HS12 uC, but if it has on-chip timer counter blocks, then yes, that would be a good way to capture the period data for your waveform, and then you can calculate the frequency from that. With a small uC, you may want to use a look-up table to do the inverse function from period to frequency.

 

[ravenprp]

Yes, there are ICs that are specifically designed for measuring periods between rising edges. These ICs are called "period counters" or "pulse width measurement ICs". They work by using a timer or counter to measure the number of clock cycles between two rising edges of a signal, and then converting that into a period measurement.

The Motorola HS12 microcontroller does have input capture ports that can be used for measuring periods. These ports can be configured for different modes, including pulse accumulation, which allows you to measure the time between multiple rising edges and accumulate them to get a more accurate period measurement.

You can use transistors to multiplex between frequency and period measurement, but it may be easier and more accurate to use a dedicated period counter IC. This will also free up your microcontroller to perform other tasks.

Make sure to carefully read the datasheet of the HS12 to understand the capabilities and limitations of the input capture ports and how to configure them for pulse accumulation. You may also want to consider using an external crystal oscillator for more accurate time measurements.