Rockwell Automation GMLC Reference Manual - Manual (Page 773)

Publication GMLC-5.2 - November 1999
736 Using the RIO Adapter Option
The returned values are stored in word pairs 0, 1 through 2nn – 2, 2nn – 1
(where nn is the number of items read) in signed BCD format. The least
significant word of the returned value is stored in the lower numbered
word of the data file and the most significant word in the higher numbered
word. Since each 32-bit value is stored as two 16-bit words, 2nn + 1
words in the data file are used.
Word-Swapped 32-bit Floating Point Format
When the most significant digit of word 2 in the BTW data file is 7,
values are transferred as IEEE-format 32-bit floating point values. In the
PLC data file, each 32-bit floating-point value is stored as two contiguous
16-bit integers. This format is identical to the 32-bit floating-point format
described earlier except for the order of the words in the data files. See
32-bit Floating Point Format in this chapter for information on the range
and precision of values.
Word-swapped 32-bit floating-point values cannot be directly converted
to or from floating point format in the PLC using the copy (COP)
instruction. This format should not be used for transferring PLC floating
point values to or from the motion controller.
If the PLC is sending data to the motion controller, the remainder of the
BTW data file (words 3 through 2nn+2, where nn is the number of items
to be sent) contains the values of the specified items, and the last word
(word 2nn+3) is the end-of-block delimiter, as shown below.
!
ATTENTION: Do not use Word-Swapped 32-bit Floating-
Point format to transfer PLC values to or from the motion
controller.