User`s manual

DSM314 COMM REQ
GFK-1742A Appendix B DSM314 Communications Request Instructions B-21
B
In the example above, when switch %I00001 is closed, the Binary Coded Decimal (BCD) value in
BCDINP (%I00017-%I00032) from a BCD Operator Input device is converted to an integer value
(by the BDC4 TO INT instruction), and the integer value is placed in register %R00150. Next,
%R00151 is cleared to zero by the BLK CLR instruction. Note that on the output of the BCD4
TO INT instruction, %R00150 is a single integer value. However, when %R00150 is used as an
input (IN1) for the double integer Multiply instruction (MUL DINT), the CPU automatically
combines it with the next %R address (%R00151) to form a double-integer value. Word
%R00150 becomes the Least Significant Word, and %R00151 becomes the Most Significant
Word in this double-integer word. The MUL DINT instruction multiplies the value in
%R00150/%R00151 by 1000, and places the result in double word %R00208/%R00209
(DBL_WRD).
When used this way, %R00151 is called an “implied address” since it is not shown on the screen.
Be aware that you must not use %R00151 for any other purpose (it should be held to a value of
zero); otherwise, the value placed into %R00150 from the BDC4 to INT instruction would be
altered. The same principle applies in the case of double word %R00208/R00209. Here, the use
of %R00209 is implied by the fact that %R00208 is displayed as the output of the Double Integer
Multiply (MUL DINT) instruction. So %R00209 should be reserved for this use only.
In this rung, the MUL DINT instruction performs two functions: (1) it converts the value in
%R00150 from single integer form to double integer form, and (2) it scales the value in
%R00150/%R00151 by multiplying it by 1000. If scaling had not been desired, a value of 1
would be used instead of 1000 at IN2 of the MUL DINT instruction; this would provide
conversion to double integer without changing (scaling) the value.
The Communications Request Instruction
The next figure shows the Communications Request (COMM REQ) instruction. The IN input
contains the address of the first word of the command block. The SYSID input contains the rack
and slot number (rack 00, slot 07) of the DSM314 targeted by this COMM REQ. The TASK
input is always zero for the DSM314. The FT output connects to a coil (%M00295) that will be
energized if a fault is detected.