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--- plc:m88_m89_stop_motion_from_plc_if_input_pin_activated [2018/09/25 13:12] – skirillov
+++ plc:m88_m89_stop_motion_from_plc_if_input_pin_activated [2018/09/25 18:39] – skirillov
@@ Line 14: / Line 14: @@
 This procedure can be handled in Hardware PLC. We offer M88 and M89 PLC procedures which do this job as a standard procedure. However, it can be customized easily according to customer needs.
-<code C M88.plc>
-//Watch on given sensor number, Soft Stop if sensor triggered
-//used for homing, surface measure, tool length measure etc
+A source code for M88 PLC procedure is shown below
+<code C M88.plc>
 main ()
 {
@@ Line 23: / Line 23: @@
   input=eparam&0xFFFF;	//P-parameter
   state=eparam>>16;	//L-parameter
-  timer=0;
   message=PLCCMD_MOTION_CONTINUE;
@@ Line 48: / Line 47: @@
 };
 </code>
+Input pin number and pins state (normally opened/closed) comes from G-code P/L parameters in **eparam** internal variable.
+Pin number comes in P-parameter and pin state in L-parameter.
+  * L=0 means the procedure waits logical "0" on selected input pin
+  * L=1 means the procedure waits logical "1" on selected input pin
+Example:
+<code>M88 P7 L0 (The procedure will wait "0" level on input pin #7)
+G90 G0X-1000 F300</code>
+<code>M88 P3 L1 (The procedure will wait "1" level on input pin #3)
+G90 G0Y300 F100</code>
+A two-lines block to decode Input pin number and a pin state from **eparam** variable is shown below
+<code C M88.plc>
+  input=eparam&0xFFFF;	//P-parameter
+  state=eparam>>16;	//L-parameter
+</code>
+After input pin number and state is decoded, the PLC procedure sends to the Motion controller a command to start next G-code line which is supposed to be a G0-positioning line.
+<code C>
+  message=PLCCMD_MOTION_CONTINUE;
+  timer=30;do{timer--;}while(timer>0);</code>
+Then the PLC procedure tests selected pin and is waiting till the pin comes to the given state (depends on L/state parameter)
+The test code is wrapped in **do{}while;** loop.
+<code C>
+  ready=0;
+  do {
+    a=portget(input);
+    if (state==0)
+    {
+      if (a==0) {ready=1;};
+    };
+    if (state!=0)
+    {
+      if (a!=0) {ready=1;};
+    };
+  }while(ready==0);
+</code>
+After the pin came to the given state, the PLC sends to the Motion controller to skip the current motion command and load the next.
+<code>
+  message=PLCCMD_MOTION_SOFT_SKIP;
+  timer=30;do{timer--;}while(timer>0);
+</code>
+There are 2 scenarios how to Stop the current motion.
+  - Immediate STOP (abort pulses generation right away)
+  - Soft STOP (do soft deceleration with given deceleration time, programmed as **Soft stop time, s** in Configuration settings of the myCNC control software.
+If motion speed is low and you need to find a precise position of input pin triggered you would need **Immediate STOP**. However, if motion speed is high and you need to find the first estimate, Immediate STOP would be harmful for machine mechanics and **Soft STOP** might be more preferable.
+The Immediate of Soft stop can be choosen by sending PLC message to the Motion Controller
+^ Message Code ^ Value ^ Description ^
+| PLCCMD_MOTION_SOFT_SKIP | 1003 | Soft stop and jump to the next command |
+| PLCCMD_MOTION_SKIP | 1002 | Immediate stop and kump to the next command |
+M88.plc procedure does **Soft Stop** if a input pin activated.
+M89.plc procedure does **Immediate Stop** if a input pin activated.
+The only difference between M88 and M89 procedures are message to the Motion controller to skip current motion.
+for M89.plc the code is
+<code>
+  message=PLCCMD_MOTION_SKIP;
+  timer=30;do{timer--;}while(timer>0);
+</code>
+A complete source for M89.plc is shown below
+<code C M89.plc>
+main ()
+{
+  input=eparam&0xFFFF;	//P-parameter
+  state=eparam>>16;	//L-parameter
+  message=PLCCMD_MOTION_CONTINUE;
+  timer=30;do{timer--;}while(timer>0);
+  ready=0;
+  do {
+    a=portget(input);
+    if (state==0)
+    {
+      if (a==0) {ready=1;};
+    };
+    if (state!=0)
+    {
+      if (a!=0) {ready=1;};
+    };
+  }while(ready==0);
+  message=PLCCMD_MOTION_SKIP;
+  timer=30;do{timer--;}while(timer>0);
+  exit(99);
+};
+</code>