TIA Portal V13 - Overwriting tags start values and retaining them

2 posts in this topic

In my program my program tags largely exist in a couple of a data blocks.  There are a number of tags in there that the operator may need to get to in order to change the value, so for alarms the high and low alarm and trip levels (so that is 4 tags per channel), or for the scaling calibrations the gain and offset values.  

I am struggling to get my head around ‘Start Value’, Default Value’, ‘Retain’ and ‘Setpoint’ values.  I have mapped over the alarm, trip and calibration tags to the HMI and can change the values with a mapped I/O field, but when I go live I can see that these values are just held in the ‘Monitor Value’.  Should the PLC go off-line then it will then go back to the default or ‘Start Values’.  I guess what I’m asking is how can I have an operator with access to the HMI, permanently overwrite a tag starting value that the PLC will hold in its non-volatile memory?

as always, cheers for any pointers.

Share this post

Link to post
Share on other sites

I think I understand your question but it would help tremendously if you could post a screenshot of what you are talking about. I think you are describing columns in the data block ('start value', 'default value', 'retain', 'setpoint'). Correct? Does the 'retain' column have data in it or is it just a check box? From what I remember it is a checkbox. A check in this column will preserve the data for that address during a power off event. Consult your manual. I recollect that there is a limit of how many addresses can be kept retentively.

1 person likes this

Share this post

Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now