Rockwell Automation 1771-QB Linear Pos. - Manual (Page 221)

Data Formats
Appendix H
HĆ4
A sign bit is placed in each word to allow negative binary numbers even with
the first word zeroed. Simply signing the first word in this case would not work
in binary mode because a word with a value of zero and the sign bit on (i.e., a
negative zero) is not equal to zero in the 16-bit 2’s complement system.
If the first word of a negative number is zero, turn on the sign bit in the second
word. For negative numbers that use both words, the use of the sign bit in the
second word is optional (see example).
Table H.B gives several examples of how you would enter BCD and binary
positions.
Table H.B
Binary and BCD Positions
Binary Format BCD Format
Position 1st Word 2nd Word 1st Word 2nd Word
+60.000 in 60 0 0060 0000
+1524.00 mm 152 400 0152 0400
+0.999 in 0 999 0000 0999
+9.99 mm 0 999 0000 0999
Ć60.000 in Ć60 0 8060 0000 or 8000
Ć1524.00 mm Ć152 400 or Ć400 8152 0400 or 8400
Ć0.500 in 0 Ć500 0000 or 8000 8500
The Linear Positioning Module supports the full range of values from -32,768
to 32,767 in the second word of the setpoint position, positioning error and
zero-position offset parameters, when using binary format.
This flexibility means that you can often enter the same parameter value in
different ways. You must still use two words in binary format if your numbers
fall outside the 32,767 to -32,768 range.
For example, to enter a setpoint of 31.999 you could either:
enter the value 31 in the first word and 999 in the second
or
leave the first word zeroed and enter the value 31,999 in the second word
Both methods result in a setpoint value of 31.999.
Double Word Position Format