Differences

This shows you the differences between two versions of the page.

--- plc:plc [2019/10/18 11:27] – ivan
+++ plc:plc [2020/09/04 14:15] – ivan
@@ Line 3: / Line 3: @@
 ====== PLC ======
-PLC - programmable logic controller.
+PLC stands for "Programmable Logic Controller".
 PLC controller can load and run small binary programs (PLC procedures). PLC procedure should be written in a simplified C-like language, compiled and stored in PLC controller memory to be ready to run. myCNC software includes [[plc:plc_builder|PLC Builder]] - tiny IDE (Integrated Development Environment) to create and modify PLC procedure source files, compile them to binary code and upload it as RomFS iso image disk to PLC controller memory.
@@ Line 32: / Line 32: @@
 === PLC Language ===
-  * PLC operates with 32 bits integer values only. Floating point operations don't work in PLC.
+  * PLC operates with 32 bits integer values only. Floating point operations don't work in PLC (typically need to use coefficient conversions to allow for more granular control).
   * There is no need to declare variables. There is very limited space of 32 elements for variables.
   * There a number of pre-defined variables in the PLC
-    * eparam - External Parameter variable. A short manual on eparam is available here: [[plc:plc:eparam|PLC - eparam]]
+    * eparam - External Parameter variable. A short manual is available here: [[plc:plc:eparam|Eparam]]
     * **proc** - variable is used to identify a process running in the PLC. \\ The value is sent to the CNC control software and can be used to display Current PLC state (like Idle, Ignition (for plasma cutting), preheat (gas cutting), Tool change, Probing etc)
     * **timer** - value can be used as time counter inside PLC procedure
@@ Line 84: / Line 84: @@
 ^ Address ^ Description ^
 | 20000...20100 | Print variable value in myCNC control message widget for debugging purpose. Values written to this registers will be printed in myCNC control software in Message widget {{mycnc:mycnc-print-variable-001.png?600}} |
+It is possible to access the state of the output via gvarget commands from within the PLC process:
+<code>a=gvarget(0x400); //OUT0
+b=gvarget(0x407); //OUT7</code>
+Starting from 0x400 to represent OUT0, this is a hexadecimal system that is simple to convert to dotted decimals (through the likes of a simple reference site [[https://www.hexadecimaldictionary.com/hexadecimal/0x400/|here]]). Thus, for example, //gvarget(0x40d);// will return the state of Output #13.
 === The hardware access registers ===
@@ Line 162: / Line 170: @@
 | <code>__HANDLER_GCODE_START</code> | The procedure executed just before the myCNC software run g-code (after pressing PLAY button) |
 | <code>__HANDLER_GCODE_STOP</code> | The procedure executed just after the myCNC software finished g-code running (after pressing STOP/PAUSE button) |
+Variables used in Software PLC:
+^Variable^Use^Example^Comment^
+| 100020 | Jog the selected axis (100020 through to 100027) | //gvarset(100020, 100);// | Negative values are not accepted, use 0-X (for example, //gvarset(100020, 0-100);//)|
+| 100040 | Launch a Hardware PLC from within a Software PLC | //gvarset(100040, 607)//; | This will launch Hardware PLC M607 |
+| 100041 | Eparameter to feed into the Hardware PLC being launched using 100040 | //gvarset(100041, 333);// | Used before //gvarset(100040, 607);//, this will set eparam=333 |
   * [[software_plc_examples|Software PLC Examples]]