Rockwell Automation 1336T Function Block Prog. Manual, Series A/B - Manual (Page 98)

Function Block Library 4–36
1336 FORCE — 5.9 August 1995
Bit 31 is the sign bit, the most significant bit for 32 bit values. For 16
bit values, bit 15 (the sign bit) is the most significant bit.
EXAMPLES Example 1 EXAMPLE 2
In 1 32767 3
In 2 32767 32767
Out LSW 1 32765
Out MSW 16383 1
OUTPUT VALUE 1073676289 98301
Example 1 — Double Word Output Value = 1073676289 = 32767
×
32767
16383
dec
1
dec
3FFF
hex
0001
hex
Most Significant Word
Node 3
Least Significant Word
Node 2
Important: The output range of the multiplied values can be critical. Should only one
output word (LSW node) of the MULTIPLY block be used, it will appear to
roll over or under if the product exceeds
±
32767.
+ 16383 (Upper Waveform) "
t1 "
MULTIPLY
Out LSW
"
MULTIPLY input "
+ 32767 (Upper Waveform) "
0 (Upper Waveform) "
0 (Lower Waveform) "
"
– 32767 (Upper Waveform)
+ 32767 (Lower Waveform)
– 32767 (Lower Waveform) "
In the Upper Waveform above, the MULTIPLY In1 input (node 0), is
multiplied by an In 2 (node 1) value of 2. As the In1 value increases beyond
16383 (time t1), the product increases beyond + 32767. Although the Out
LSW output (node 2) has a range of 0 to 65535 (0 to FFFF
hex
), the analog
input has a single word signed range of
±
32767. When the input reaches
16385, the multiplied output of 32770 (8002
hex
) is interpreted by the signed
analog output parameter as having a value of – 32766 which makes it
appear to roll over.
MULTIPLY
(continued)