Internet PLC Forum

Hi Gary,

Thanks for the excellent explanation. We couldn't have done it any better than what you did.

Just add a note to someone new to TBASIC - the variables represented by INPUT[] and OUTPUT[] are stored in internal memory and they are normally only synchronized to the physical I/Os at the end of the ladder logic scan. So it will be a mistake to monitor an input inside a TBASIC loop because these internal memory do not change state:

E.g.
WHILE 1
   IF TESTIO(IN5) EXIT: ENDIF
ENDWHILE

The PLC program will be stuck in the WHILE loop because IN5 will never be turned ON.  You can force the internal I/O to be updated using the REFRESH statement:

WHILE 1
   IF TESTIO(IN5) EXIT: ENDIF
   REFRESH
ENDWHILE

REFRESH statement will update the memory INPUT[] to the states of the associated 16 physical inputs. There is a penalty of I/O scan time being used each time you run the REFRESH statement (about 2ms for a FMD or Fx PLC, shorter for Nano-10) so you want to use it only when necessary.  Letting the ladder logic monitor changes in input and use it to trigger custom functions for TBASIC processing will normally be a lot more efficient than monitoring it inside a WHILE loop.

We have never encountered the issue you showed on your screen shot.

It is likely has something to do with the graphic driver.

You mentioned that the TRiLOGI screen display fine on your laptop screen. Does your laptop has 4K screen built-in or it is driving an external 4K monitor? Does it happen when you move the iTRiLOGI windows from your laptop screen to the 4K screen when resolution changed?

You may want to try to disable some graphic acceleration in graphics card as these sometime introduce incompatibility.

Are you using 32-bit Java JRE?

If you have two 16-bit value, say lower 16-bit in DM[1] and upper 16-bit in DM[2], then you can form a 32-bit number by defining a variable in Javascript such that:

var data32 = DM[2]<<16 + DM[1]

You will need to know some javascript and jquery so that you can insert the value of the variable "data32" into the 0.htm page from the javascript file M.JS (in particular the refreshScreen() function) so that it will display on the 0.htm page.

The FMD1616 PLC has an I/O scan time of 2ms. The program scan time depends on how your program is written and can vary.

If you only run a couple of rungs of ladder program and it does nothing more than just count pulses it may be able to handle up to 200 Hz. But if you have custom function that may take up long time (e.g. communicating with 3rd party devices via serial or Ethernet port) then the time varies. It is best if you use a separate FMD88-10 which has 4 interrupt inputs and 4 regular inputs and if this slave PLC does simple counting you should be able to handle your 30 to 50Hz pulse inputs.

Thanks for the great contribution to the community!

Gary's suggestion is what we would normally advise users too.

The good news is that since firmware version r70 (on FMD and Nano-10) and on all the Fx series since firware version F90.0 we have implemented stepjog function which is to STEPMOVE with either &H7fffffff or &H80000001 for infinite rotation in positve or negative directions, respectively.

Hopefully this answers to your question. This should have been included in the manual. Will bring this up with the staff who maintain the manuals to include in future editions.

The FMD, Nano-10 and Fx series of PLC can directly read standard quadrature encoder inputs. Each high speed counter only needs two digital inputs (see Chapter 6 on the mappings to the digital inputs).

However, if you are trying to read a specialty encoder using ladder logic it may not be fast enough to process in real time due to the time lag in the I/O scan (about 2ms for FMD and Fx PLC. Much shorter for Nano-10 since there is no expansion I/O) which means that you may miss some rising / falling edge.

You may also try to use the interrupt inputs to handle the specialty encoder.