Fast digital inputs TM172

[otrotabi]

I need help regarding how to use TM172 fast digital inputs. As far as I know, digital inputs DI1 and DI2 in the whole line can either be used as regular digital inputs or as fast inputs.

I am sure this is documented somewhere, if so please let me know where to find the documentation.  I have checked all the documents I have and could not find it.

Following the convention followed on the published TDVAs I am naming inputs as per the following pic.

I then later reassign them to logical variables within a program called Physical_to_logical_inputs, the same concept used in TDVAs.

So, let´s say I add these new variables like in the picture and add these lines to Physical_to_logical_inputs program:

Status_udiCount1 := FI_Counter1;

Status_udiFreq1 := FI_Frequency1;

Is that all that it takes? In case I only need one fast input, for example DI1, is DI2 still available as a regular input?

What is the unit of FDI Frequency ? 

What do FDI*_value and FDI*_reset_counter mean  and how are they used ?

[FedericoM · Accepted solution]

Hi,

here below the answers to your questions:

Is that all that it takes?

Yes, it is

In case I only need one fast input, for example DI1, is DI2 still available as a regular input?

Considering che common input, DI2 can be used as regular input

What is the unit of FDI Frequency ? 

[Hz/10]

What do FDI*_value and FDI*_reset_counter mean  and how are they used ?

FDI*_value is the current status of the input (like when you use it as regular input)

FDI*_reset_counter if set to true allows to reset the number of counted pulses

[otrotabi]

😀

Pretty simple actually.  Thanks.

In the previous post you said :"The frequency is the one of the last period, so you might need to post filter it." Could you explain a little further ?

I noticed there´s a small lag between the time the signal in my scope goes to gnd and the time frequency reads 0 in the PLC. For this application it has no importance but I think that it eventually become important for other uses. Is that what you mean by post-filtering the signal? What kind of filters may be used ?

As a side note: is a pull up resistor advised  ?