Rockwell Automation GMLC Reference Manual - Manual (Page 755)

Publication GMLC-5.2 - November 1999
718 Using the RIO Adapter Option
Up to 30 sequential user variables or cam table points can be transferred
in any one block transfer using 32-bit integer numeric format since each
block transfer is limited to a maximum of 64 words, as shown by the
following formula:
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.
The returned values are stored in word pairs 0, 1 through 2nn – 2, 2nn – 1
(where nn is the number of items read) in 2s complement format. The
most significant word of the returned value is stored in the lower
numbered word of the file and the least significant word of the returned
value in the higher numbered word. Because each 32-bit value is stored as
two 16-bit words, 2nn + 1 words in the file are used.
30 Items 2
Words
Item
----------------
×
3 Header Words End-of-Block Word
64 Words =
+ +
RIO Adapter Block Transfer Read
32-bit Integer 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+1
2 nn+2
Last Data Item Value Most Significant Word
Last Data Item Value Least Significant Word
2 nn+3 End-of-Block Delimiter (000D Hex)