Hi All,

Over the past days I have been struggling with storing analog input values in a fast buffer. Some info First:

• Operating System: Windows 10
• TIA Version: v16
• Service pack and update: do not know where to find this
• Hardware Modules numbers: CPU 1214C DC/DC/DC with an SM 1231 AI4 (6ES7 231-4HD32-0XB0) 

What I try to do:

Store the (processed) value of an analog input over a short period of time (+/- 1 second) into an array, and then process these values.

What I alread did:

1. Created a cyclic OB (OB123) that takes the Analog input (IW500 in my case) and converts it in multiple steps from raw value (0-27648) to the meaningful measurement (distance stored in a Real)
2. After many different trials: Used LGF_FIFO to put incoming measurements into an Array of 1000 Reals that is defined in a DB.

The Problem I Run into:

From the documentation, I learned that LGF_FIFO puts the value at "Item" into "Buffer" only when a positive edge is detected at "Enqueue". Initially I tried using the build in clock signals to cyclically send a positive edge to the FIFO block so that it saves the measurement. However the highest frequency clock signal is 10 hz, which means 100 ms between each measurement. 

Using Traces I have observed that the analog input module is providing new measurements at a much high rate (roughly every 3 ms). In order to capture the full data I tried making an own pulse-train, using this example. This yielded a working 1 ms pulse train. When I supply this signal to the FIFO buffer and check the number of points in my array after roughly 1 second of measuring, I only find roughly 400 samples in the buffer instead of the almost 1000 that are expected. It seems to me that the FIFO buffer has a performance limitation.

Some Questions:

1. Does anyone know if there is an inherent performance limit on LGF_FIFO, that prevents using at up to 1 ms cycles?
2. Is there a better/more elegant/built-in way to obtain a high frequency pulse train? 
3. Is there a better/more elegant/buit-in way to buffer analog input values over some period of time? I can imagine this is usefull for many applications?
4. I know there are High Speed Counters (HSC) availible in my PLC. I only found the function blocks that can be used to control/configure this counters. Is there a way to actually get some sort of pulsed signal from these counters into my Organizational Blocks?

Thank you all very much for your responses.

OK. You showed some devotion. Now you can leave it.

Use a Cyclic Interrupt @ 1 ms. If you have no better idea for a buffer than the LGF_FIFO, that's ok. Just call it TWICE (yes, TWO consecutive calls) the first time with Enqueue = FALSE, the second with TRUE.

HSCs are ment for completely different scenarios.

Thank you jacek and Einstein, I will look into the approaches you propose and get back with what I find.

Regards,

Rik