User`s manual

B-20 Motion Mate™ DSM314 for Series 90™-30 PLCs User's Manual – January 2001 GFK-1742A
B
Locic for Parameter Data (not Shown)
Additional logic will be required to load your data into registers %R00208 - %R00239 so that it
can be sent to the DSM314 parameters. (The value in double word %R00208/%R00209 will be
sent to Parameter 1, the value in %R00210/%R00211 will be sent to Parameter 2, and so on, until
finally, the value in %R00238/%R00239 will be sent to Parameter 16.) The method to be used for
loading the data into these registers depends upon your application. If the data values will not
change, constants can be moved into the registers using Block Move and/or Move instructions. If
the values are to change, they could be moved into the registers from an operator interface device.
Handling Double Integer Parameter Values and Input Value Scaling
The data in our single precision registers (16 bits) needs to be converted to double-integer (32
bits) form since the DSM’s parameters are double-integer size. A convenient way to do this is to
use a Double Integer Multiply (MUL DINT) instruction to move input data into the PLC registers
whose contents will be sent to the DSM. There are two possible advantages to this approach:
•
This is an easy way to convert single integer registers to double-integer form.
•
It lets you easily scale the input values if you should need to. The term scaling refers to
multiplying and/or dividing a value to create a new value that is proportional to the original
value. For example, multiplying an input value by two, then dividing it by 3 would result in
an output value that is always 2/3 the size of the input value. Scaling is often required in a
servo system to match the actual distance moved to the distance commanded. It doing so, it
provides the function of an “electronic gearbox.” It can be used to allow for gear ratio,
ballscrew pitch, encoder resolution, and customer input value preference.
In the example below, the integer value from an Operator Input device (a 4-digit BCD
thumbwheel switch) will be multiplied by a factor of 1000, then placed into the double-integer
word %R00208/%R00209 (for Parameter 1).