Rockwell Automation GMLC Reference Manual User Manual
Page 768
Publication GMLC-5.2 - November 1999
Using Block Transfers
731
When received by the motion controller, the two integers representing
each value are concatenated into the original 32-bit floating-point value.
Unlike the preceding fixed-point (integer) formats, 32-bit floating-point
format does not require specification of the number of decimal digits in
the value. Thus, the second most significant digit of Word 2 in the BTW
data file (digit d) should be set to 0 as shown above. With 32-bit floating-
point numeric format, the largest value that can be represented is
±1 x 10
38
and the smallest is ±1 x 10
–
38
.
Up to 30 sequential user variables, or cam table points, can be transferred
in any one block transfer using 32-bit floating-point numeric format
because each block transfer is limited to a maximum of 64 words, as
shown by the formula below:
If the PLC is getting data from the motion controller, no item values need
be specified in the BTW data file and thus the end-of-block delimiter is
word 3 (nn = 0). The returned data is stored in the integer (N) file
specified in the BTR. After completing the BTR, this file contains the
returned values, as shown below.
RIO Adapter Block Transfer Read
32-bit Floating-Point Returned Values Data File Format
Word
Description
0
1
First Data Item Value Most Significant Word
First Data Item Value Least Significant Word
2
3
Second Data Item Value Most Significant Word
Second Data Item Value Least Significant Word
…
…+1
Next Data Item Value Most Significant Word
Next Data Item Value Least Significant Word
2
nn-2
2
nn-1
Last Data Item Value Most Significant Word
Last Data Item Value Least Significant Word
30 Items
2
Words
Item
----------------
×
3 Header Words
End-of-Block Word
64 Words
=
+
+