Delta MMC120 - Manual (Page 66)

Quantum Programming Hints MMC120 Linear Motion Control Module
66 Delta Computer Systems, Inc. 360/254-8688
QUANTUM PROGRAMMING HINTS
The Programmable Controller is responsible for storing the initialization parameters used by the MMC120 and
initializing the Motion Control Module with those parameters.
The MMC120 provides a STATUS word for each axis. If an error bit is set in the STATUS word, the
Programmable Controller is responsible for shutting down the axis drive power. It must have a watchdog
timer that will shut down the drives if a time-out occurs.
Write to the MMC120 only once per segment, otherwise the newest data will overwrite the previous data.
See the demo program on the DCS120 disk for ladder logic examples.
Error Handling
The MMC120 reports errors to the Quantum Controller within one millisecond of detection. Errors are
reported by setting bits in the affected axis' STATUS word and turning on the appropriate Front Panel LEDS.
The Programmable Controller is responsible for checking errors by reading the STATUS words. It is up to the
Programmable Controller to determine what should be done if an error is detected.
The system must be able to shut down the axis drive power using a normally open output which is held closed
when the system is running. This contact should be in series with an operator emergency off button. If power
to the rack is lost, the contact will open and the axes will stop. If an error occurs in the MMC120 the contact
can be deactivated, which stops the axes. Usually the Programmable Controller will not take so drastic a step
until it has determined that all control is lost. An 'H' (HALT) command to the axis with an error can take care
of most error conditions.
When two axes are making a coordinated move and one axis starts moving slower than it should, it is best to
issue a HALT command to both axes to stop all movement until the problem with the faulty axis has been
resolved.
You can also use AUTO STOP for error detection by setting the appropriate bits in the SOFT STOP the
HARD STOP bytes corresponding to the error bits in the STATUS word. See AUTO STOP (page 31) and
STATUS (pages 38-40).