Rolling data buffer in s7-300

I am currently working on a project that utilizes a pair of digital water flowmeters.
Each flowmeter continuously generates a single pulsed output, the frequency of which is directly proportional to the flow through the meter.
I plan to use the frequency input mode of the PLC (S7 313-c) and buffer the returned value over a number of sample cycles.
Ideally, I would like to have a rolling 20 cycles stored. I will then sum and average the buffer to give a value to be used in further calculations.
When the buffer is full, the oldest sample can be "lost" as a new sample enters.
My question is this (and please excuse my ignorance if the answer is obvious!): what would be the best method of generating the buffers?

What data type will you be storing in the buffer - int, dint, real ?

Here's a simple example assuming the buffer contains INTs. Define your buffer(s) in the STAT area of a function block.

Thankyou. I'm sure that will do the trick. I will have to modify it slightly as I will be using multiple DBs but this is easily done.

L D[AR2 said:

Here's a simple example assuming the buffer contains INTs. Define your buffer(s) in the STAT area of a function block.

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