Rockwell Automation GMLC Reference Manual - Manual (Page 760)

Publication GMLC-5.2 - November 1999
Using Block Transfers 723
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) data file
specified in the BTR. After completing the BTR, this file contains the
returned values, as shown below.
The returned values are stored in words 0 through nn – 1 (where nn is the
number of items read) in 2s complement format. Because each value is
stored as a single 16-bit word, nn words in the file are used.
The returned values are converted from the floating-point format used in
the motion controllers to 16-bit 2s complement integers before being sent
to the PLC. This conversion is performed in the motion controller by
multiplying the floating-point values by the following and truncating any
remaining fractional part:
10
(Number of Decimal Digits)
The number of decimal digits (digits to the right of the decimal point) for
the returned values is fixed for all items in a given BTR, and is specified
by word 2 in the BTW data file used to request the data from the motion
controller. To recover the original value, the PLC must divide the received
integer value by:
10
(Number of Decimal Digits)
RIO Adapter Block Transfer Read
16-bit Integer Returned Values Data File Format
Word Description
0
1
2 First Data Item Value
Second Data Item Value
Third Data Item Value
nn-1 Last Data Item Value
nn End-of-Block Delimiter (000D Hex)