Rockwell Automation 999 IMC S Class Compact Motion Controller (Cat. No. 4100-999-122) - Manual (Page 39)

Technical Overview 3-9
Publication 999-122 - January 1997
Velocity feedforward is very useful in electronic gearing applications,
since no position error between the master and slave axes exists with
mechanical gears. Using velocity feedforward also allows the position
loop integrator (I Gain) to respond more quickly to changes in speed.
CPU Watchdog The IMC-S/23x provides a CPU Watchdog that monitors the health of
the motion control microprocessor. In the event of a processor
malfunction or other fault, the CPU watchdog is immediately disabled.
To reset the Watchdog, the IMC-S/23x must be reset, either by cycling
power, or by pressing the Reset button on the front panel.
An LED labeled "System OK" is provided on the IMC-S/23x front
panel to visually monitor the state of the CPU watchdog. This green
LED is lit under normal operation, and goes out when the watchdog is
deactivated. A relay driven by the CPU watchdog provides normally
open and normally closed contacts on the Watchdog connector for
wiring into the machine’s E-Stop string or other fail-safe circuit.
Software Overtravel Limits The IMC-S/23x can be configured to range check the command
position of each axis to ensure that the axis is operating within its limits.
These software travel limit values are fully programmable. When an
overtravel condition occurs, the IMC-S/23x either disables the
feedback loop and disables the amplifier, or decelerates the axis to a
stop. In either case, further motion in the offending direction is
inhibited.
Serial Communication Serial communication with the IMC-S/23x is via either an RS-232C or
RS-422 serial link to one of two ports. If configured for RS-232C,
operation up to 19.2K baud is possible, while ports configured for
RS-422 can operate at up to 128K baud. A PC/AT-compatible 9-pin
D-type connector is provided for each serial port on the front panel. In
general, the GML software development system for application
programming is connected to serial port A while a serial operator
interface device or runtime display is connected to serial port B.
The IMC-S/23x can be configured to operate in Multidrop Mode
allowing up to eight controls to share a single RS-422 communications
link. This is accomplished by using two special non-echoed commands
to activate individual units to respond to commands issued by the
operator interface device or host computer. Each IMC-S/23x is assigned
its own unique address via a recessed front-panel rotary selector switch.