Delta MMC120 User Manual download pdf (Page 67)

by the Motion Controller and initializing the Motion Control Module with those

parameters.

The Motion Controller provides a STATUS word for each axis. If an error bit 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 Motion Controller only once per scan, otherwise the newest data will

overwrite the previous data.

Error Handling

The motion controller reports errors to the Programmable Controller within one control

loop of detection. Errors are reported by setting bits in the affected axis’s STATUS word

and turning on the appropriate 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

that 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 motion controller 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 Halt commandtotheaxiswithanerror

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 detection by setting the appropriate bits in the SOFT

STOP the HARD STOP bytes corresponding to the error bits in the STATUS word.

MMC120 Module Problems

Problems and Solutions

Control program cannot access parameters or operate module

1. Module not configured properly—active LED off. Configure the module as a 4-

input and 4-output register module with binary format.

2. Make sure the Programmable Controller is accessing the correct I/O registers.

RedLEDS2,3,4,6,7,or8areon

This indicates the transducer is not responding to the module. Every millisecond the

module interrogates the transducer’s position. If a return response is not seen after about

two milliseconds, the internal counters overflow, and red LED 4 or 8 will be latched. If a

return response is not seen after six milliseconds, red LED 2 or 6 will be latched. If the

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Delta MMC120 User Manual Page 67