Output channel's output enabled bit

[DBeck]

How does a "Discrete on Ch1/Fn1" type output function with it's Enable Output control bit and Output Enabled status bit? 

When I use the CTRIO workbench to access the Output Functions dialog (with "CTRIO read of PLC outputs is suspended"), I can't cause the output channel's Output Enabled status indicator in that dialog to indicate off status (it won't change from indicating on), regardless of the state and manipulation of the channel's Enable Output button.

This issue has come up for me as I programmatically (via PLC logic) manipulate the Enable Output control bit to cause a preset table created using Initialize Table and Add Table Entry commands to be acted on by the output.

Thanks for any assistance.

[DBeck]

Additional elaboration:

Clearing the Enable Output control bit in PLC logic for the desired output channel doesn't appear to cause the Output Enabled status bit for that channel to be cleared.

[Greg]

Probably what you have run into is you have a preset table configured to automatically load. If you press the <Config IO...> button and go to that dialog and you have selected, say, Output 2 as "Discrete on Ch1/Fn1" then there is an extra button that will appear in the Function 1 box: <2: Preset>. If you press that button this takes you to a dialog called "Default Output Settings (Preset Mode)". This allows you to select a Preset Table for auto-loading. If you have selected a Preset Table for auto-loading (select "Load Table Table Number" with a corresponding number), then the CTRIO output (in my example, Output 2) will be selected for auto-load as "Discrete on Ch1/Fn1". What this means is when the CTRIO powers up, that particular Preset Table is loaded automatically (no Load function has to be called from ladders) AND the Output is automatically enabled.

Consequently, you do not have to use the Enable Output bit to enable the output. Also, if you happen to go into <Monitor I/O> function with the CTRIO reads of the PLC outputs suspended, you will notice the Output Enabled bit is already ON even though the <Enable Output> button is not pressed.

If you disable the Preset Mode function that automatically loads the Preset Table as described above by setting it back to "None", then you will not only have to manually enable the output (Enable Output = ON) to get it to work, you will also have to do a Load function from ladders.

[DBeck]

Thanks Greg, that's really helpful!

It's not critical to my application, but I was hoping to have a "default" preset table that would auto-load, then upon demand (via PLC logic), a new on-the-fly constructed preset table could be substituted for the auto-loaded table.  The substituted table wouldn't need to be persisted in the CTRIO's ROM (though I realize it could be).  Is there a way for me to get around the behavior I'm seeing with the Output Enable and still have this scenario of being able to substitute a new on-the-fly constructed preset table for an auto-loaded table?

[Greg]

If you load a Preset Table for that same Output (or construct one and then make that one active), then the Output Enable bit will go OFF. From that point on (until the next power cycle) it must be manually set and reset by the ladder logic. If you wanted your "auto-loaded" table back, you would have to manually load it back, and again, the Output Enable would still be manually controlled.

[DBeck]

If I follow all this, if an output is configured for auto-loading a preset table, then the output's enable control cannot be changed programmatically (active/cleared) nor changed through the CTRIO Workbench's monitor I/O enable output toggle push button, until the Load Preset Table command is performed for that output.

This new knowledge has got me thinking that since my primary design is to store the preset tables in the PLC (V memory) and push them into the counters' table buffers when the PLC moves from program to run mode (this allows me to remotely track and change the preset table data via an ECOM module), my initial thought of a "default" preset table in the CTRIO ROM is overkill and I don't see a need to auto-load preset tables.

Greg, as before, you've really explained another murky aspect of the CTRIO to me, thanks again!

[BobO]

If I follow all this, if an output is configured for auto-loading a preset table, then the output's enable control cannot be changed programmatically (active/cleared) nor changed through the CTRIO Workbench's monitor I/O enable output toggle push button, until the Load Preset Table command is performed for that output.

Cannot be changed? Well...yeah...although when I wrote it I thought of it as 'automatically enabling', not 'refusing to change'. It was done that way to allow folks to implement a simple preset table behavior without requiring code to make it work. Once you make a change to the table from code, you are in essence saying 'I got it now', after which the auto-enable is dropped.

[DBeck]

Is it the case that either an Initialize Table (0x12) or Add Table Entry (0x13) command will drop the auto-enable state, or is the Load Preset Table the only command that will drop the auto-enable?

[BobO]

Any mod to the default table...whether load, init, or edit...will clear the auto-enable and require manual enabling for subsequent operation.

[DBeck]

Thanks for all the clarification on this.  I really appreciate the great support you guys provide for your products!  Sadly it's so rare to find that with the competitors.