Rockwell Automation 57C422B 2 Axis Servo Module - Manual (Page 113)

G-1
A
PPENDIX
G
Compatibility with Earlier Versions
Stop Motion Command
If you are replacing a 57C422 module with a different version
of the same module, the Stop Motion command (Register 66
Bit 6)* may now operate differently than it did in the module
being replaced. To determine the version number of the
57C422 module you are working with, examine the label on
the side of the module. This label will reference a "B/M"
number designation, which is the version number.
The Stop Motion command has two modes of operation
which are selected by the Stop Action bit (Register 65 Bit 7).
If the Stop Action bit is off, issuing the Stop Motion command
will cause the drive to decelerate to a stop at the rate
specified when the motion was started. It is when the Stop
Action bit is set, i.e., "fast stop" is enabled, that the difference
between versions of the module is important. If your
application program does not set the Stop Action bit, this
difference between versions is immaterial. If, however, your
application does set the Stop Action bit, you must note the
following.
In B/M-57422, if the Stop Action bit is set when the Stop
Motion command is issued, the drive will try to stop
immediately with no limit on the rate of deceleration. This can
cause the drive to turn off because of position or velocity
error, and then coast to a stop.
In B/M-57422-1, B/M-57422-1A, B/M-57422-1B, and
B/M-57422-2, the Stop Action bit works differently. If the Stop
Action bit is set when the Stop Motion command is issued,
the drive will control the rate of deceleration. This control can
only be accomplished through the deceleration rate used by
the Home command. For this reason, if your application
program does a Stop Motion command with the Stop Action
bit set you MUST first perform a Home command. If this is
not done, the deceleration rate for the "fast stop" will be zero
and the drive will not stop.
For applications that don’t normally use the Home command,