Rockwell Automation 8520-GUM 9/Series CNC Grinder Operation and Programming Manual Documentation Set - Manual (Page 310)

Introduction to Programming
Chapter 10
10-32
(4) End of Program, Tape Rewind (M30)
If you execute a program from control memory, the M30 code acts the
same as an M02. The control stops program execution and enters the cycle
stop state. The program is reset to the first block and a <CYCLE START>
begins part program execution over again (see M99 for auto cycle start).
If executing a program from an external device (such as a tape reader),
when the control executes M30, it stops program execution and
automatically rewinds the tape to the beginning of the program just
executed. After the tape is rewound, the control enters the cycle stop state.
A <CYCLE START> begins part program execution over again (see M99
for auto cycle start).
With some machines, the M30 code can also result in a spindle and coolant
supply stop. For details, see the instruction manual prepared by your
system installer.
(5) Overrides Enabled (M48)
When M48 is executed, the feedrate override, rapid feedrate override, and
the spindle speed override functions become effective. Normally, these are
enabled on power-up without requiring this M code to be executed. An
M48 cancels an M49 and your system installer can choose which is active
upon power-up.
(6) Overrides Disabled (M49)
Use the override disable M code (M49) to ignore any override set by the
operator on the MTB panel. When the control ignores the override setting,
the axis feedrate, rapid feedrate, and the spindle speed override values are
all set to 100%. An M49 cancels an M48 and your system installer can
choose which is active upon power-up.
(7) Constant Surface Speed Mode Enable (M58)
M58 cancels M59 mode and allows the control to recognize programmed
G96 constant surface speed mode with S words. The spindle resumes the
speed it was revolving at prior to the designation of M59.
ATTENTION: Restoring the constant surface speed mode
might cause the spindle speed to increase or decrease rapidly,
depending on the grinding wheel position.