Viewing System Variables

TBASIC has many internal numeric and string data which can be easily examined by clicking  the . button on the Simulation or Monitoring screen. When you are in On-Line Monitoring mode, the data shown are the "real-time" data captured from the PLC (of course, subject to some communication and network delay) and will be updated periodically.

These variables are organized into 4 screens which can be scrolled by  by clicking on the buttons or by pressing the left/right cursor keys. On some screens that span more than one page, you can scroll from page to page by clicking on the buttons or by pressing the <PgUp><PgDn> keys.

Numerical data can be viewed either in Decimal or Hexadecimal format. You can switch to the Hexadecimal format by clicking on the button or by pressing the <H> key.

Finally,  the button (or the <E> key) allows you to make changes to any internal variables. When you are in On-Line Monitoring mode, the changes are written into the PLC. This may be useful if you need to make temporary changes to some of the PLC's data  (e.g. set some parameters) without altering the program. It also helps in debugging your PLC software by allowing you to force some value to see the effect on the program. When you click on the button, a window will open to prompt you to enter the desired changes:

You must enter the values for the variables in an assignment format as follow: E.g.  X = 123456 timerPV[1] = 500 emLint[5] = 200

1.  View Integer Variables A to Z and ADC/DAC/PWM, RTC etc

Note:

• A to Z  and HSC1 to 3 are 32-bit variables. 
• Only HSCPV[1] to HSCPV[3] are displayed. HSCPV[4] to [8] are not visible. 
• ADC1-8 shows only analog input data captured by the last-executed ADC(n) statement.  
• Four-line LCD Display - only those statements executed by SETLCD will be displayed. LCD data displayed by the PLC will be captured and shown here during on-line monitoring mode. 
• Initial data for Date and Time are taken from the PC's clock during simulation. For on-line monitoring, these are taken from the PLC's RTC periodically.

2. View Float-point Variables

This is the second view variable screen which displays the floating-point variables A# to Z# as well as the 1000 floating-point array FP[1] to FP[1000]

You can click on the "PgUp" or "PgDn" button on the screen or use the "PgUp" and "PgDn" keys on your keyboard to scroll through all the pages to view all 1000 FP[ ] variables.

The third button: "IEEE"  - let you switch the view of the values of these floating-point variables between human readable decimal format and their actual IEEE 32-bit single precision format. In IEEE mode these values are displayed as 8 characters of hexadecimal digits.  IEEE defines some bits as mantissa and some as exponent in order to use 32-bit number to represent a wide range of float values.

If you are interested in seeing how the floating-point values are represented in IEEE format you can use the following online calculator to verify the data you observe on the screen:

http://www.h-schmidt.net/FloatConverter/

Note:  "Local Variables" as described in the "Floating-point Constants Variables and Operators" cannot be viewed from the View Variable screen as they are not global variables and hence their data changes from one custom function to another during program execution. The only way to view the local variables is to put a break point in a custom function and when the program stops at the break point with the custom function opened, the local variables can then be viewed from within the custom function editor. Please click here to view more details.

3. View Data Memory DM[1] to DM[4000]

• First row shows DM[1] to DM[10]
• Second row shows DM[11] to DM[20]
• .....
• Last row shows DM[151] to DM[160] etc.
• Total number of DM = 4000 are organized into 25 pages. During On-Line Monitoring, only DM data for the current page is monitored. Everytime you switch pages, the DM data for the new page will be captured and displayed automatically.

4. View String Variables A$ to Z$

Note:

• Each string has a maximum of 70 characters.
• A string longer than the screen width will flow into the second line. However, this does not indicate that the string contains a Carriage Return (CR) character.

5. View System Variables (Input[n], Output[n], Relay[n], Timer[n], Ctr[n], emInt[n], emEvent[n], emLint[n])

Note:

• The PLC's I/O bits can be referenced in TBASIC as 16-bit integer variables. For example. Input #1 to #16 are contained in INPUT[1]. Timer contact #33 to #48 are contained in the variable TIMER[3], etc.
  
• On the second page, the special emVariables: emInt[1] to emInt[16], emLint[1] to emLint[16] and emEvent[1] to emEvent[4] are displayed. emVariables are useful if you wish to interface to EMIT 3.0 system developed by emWare, Inc of Salt Lake City. (emEvent[1] is also used by the TLServer as an outgoing email request flag so you can observe its value here).