P/C Programming Precautions; P/C Error Handling; Key Things To Remember - Delta Computer Systems TMC 188/40 Series Manual

TMC 188/40 Motion Control Module

P/C Programming Precautions

The P/C is responsible for:
Storing the VINIT parameters used by the TMC 188/40.
Properly initializing the Motion Control Module using the VINIT V Memory locations.
Loading the MCM‟s WY registers with the correct V Memory locations.
Turning off drive power when the TMC reports an error.
Having a watchdog timer that will shut off drive power if a time-out occurs.
Issuing an 'H' or HALT command when drive power is turned off and restoring the null when
power is turned back on.
Issuing a 'P' or 'G' command to return an axis to closed loop control after a transducer error
clears.

P/C Error Handling

The TMC 188/40 reports errors within two milliseconds after they are detected. It does this by setting
a bit in the axis STATUS WORD and flashing the appropriate Front Panel LED. The P/C is
responsible for checking errors using the STATUS BITS (see page 26). It is up to the P/C to
determine what to do if an error is detected.
You can also use ESTOP and HALT to detect errors by clearing the bits in the HALT and ESTOP
masks corresponding to the error bits in the STATUS WORD. See the STATUS WORD bit definitions
starting on page 23.
The system must be able to shut down the axes drive power by deenergizing a normally open (held
closed) contact. This contact should be in series with an operator emergency off button. If power to
the rack is lost, the contact will be deactivated and the axes will stop. If an error occurs on the TMC
188/40, the contact can be deactivated, thus stopping the axes. Usually the P/C will not take so
drastic a step until it has determined all control is lost. An 'H' or HALT command for the axis with an
error can take care of most error situations.
When two or more axes are in a coordinated move and one axis starts moving slower than it should,
it is best to issue a HALT command to all the axes and stop operation until the problem with the faulty
axis has been solved.

Key Things to Remember

Retracting is always toward the transmitter end of the magnetostrictive transducer.
(TRANSDUCER COUNTS decrease while retracting.)
The last 6 inches of the transducer are usually not usable.
When the DIRECTION is 0, all positions are added to the OFFSET value. When the
DIRECTION is -1, all positions are subtracted from the OFFSET.
When the DIRECTION is 0, all positions from the zero position to the transmitter should be
thought of as negative numbers. When the DIRECTION is -1, all positions from the
transmitter to the end of the rod should be considered negative numbers.
Transducer nonlinearity may be an issue when opposing axes are used.
Delta Computer Systems, Inc. 360/254-8688
Getting Started
15