Added number of character count for not recognizing S0 and S00 command and recognizing P000,R000 and S000 only.

Marlin/src/gcode/gcode.cpp

@@ -260,11 +260,11 @@ void GcodeSuite::process_parsed_command(const bool no_ok/*=false*/) {
     }
   #endif
 
-  // Handle a known G, M, or T
+  // Handle a known G, M, or T (S,P & R from emergency parser)
   switch (parser.command_letter) {
     #if ENABLED(FULL_REPORT_TO_HOST_FEATURE)
       case 'S': case 'P': case 'R': switch (parser.codenum) {
-        case 0: break; 
+        case 0: if(parser.numchars==3) break; 
       default: parser.unknown_command_warning(); break;
     }
     break;

Marlin/src/gcode/parser.cpp

@@ -50,6 +50,7 @@ char *GCodeParser::command_ptr,
      *GCodeParser::value_ptr;
 char GCodeParser::command_letter;
 int GCodeParser::codenum;
+int GCodeParser::numchars;
 
 #if ENABLED(USE_GCODE_SUBCODES)
   uint8_t GCodeParser::subcode;
@@ -166,7 +167,12 @@ void GCodeParser::parse(char *p) {
       command_letter = letter;
       // Get the code number - integer digits only
       codenum = 0;
-      do { codenum *= 10, codenum += *p++ - '0'; } while (NUMERIC(*p));
+      numchars=0;
+      while (NUMERIC(*p)) {
+        codenum += *p++ - '0';
+        codenum *= 10;
+        numchars++;
+      }
       return;
 
       default: break;

Marlin/src/gcode/parser.h

@@ -85,6 +85,7 @@ public:
               *string_arg,                // string of command line
               command_letter;             // G, M, or T
   static int codenum;                     // 123
+  static int numchars;                     // 123
   #if ENABLED(USE_GCODE_SUBCODES)
     static uint8_t subcode;               // .1
   #endif