Rockwell Automation 1771-DA,D17716.5.13 U MNL 1771-DA ASCII I/O MODULE - Manual (Page 147)

Function of Control/Status Bits
Chapter 6
6Ć12
When operating in report generation mode, use these bits to select a BCD
delimiter. Insert a BCD delimiter before and after BCD numbers in your
message. The BCD delimiter instructs the module to convert and store
numbers in the BCD format (3 or 4 characters per word that you chose in
IW2(14-16)).
Select the BCD delimiter from any one of the following hex codes: (Refer
to the Hex/ASCII Conversion Table in the appendix C).
OA-OF
1A-1F
2A-2F 4A-4F 6A-6F
3A-3F 5A-5F 7A-7F
The module defaults to the colon (:) as the BCD delimiter if you do not
use initialization word four.
You can use the default value of IW4(10-16) only when you select three
(or fewer) initialization words. If you select four initialization words, you
must enter a value in IW4(10-16). This value cannot be the same value as
the end-of-string delimiter that you entered in IW3(10-16) or an
initialization error will occur. This applies to both functions of
IW4(10-16), BCD Delimiter, and removing the fill character.
Description: Removes Fill Character (Data Mode)
When operating in data mode, use these bits to select the fill character,
generated by the ASCII device, that the module removes. Some ASCII
devices vary the number of data characters per string, and insert fill
characters to make all strings of equal length. The module deletes the fill
character whenever encountered in the string. The module justifies the
data (changing its position), and substitutes its own fill characters for the
ones it removes.
Select the fill character to be removed identical to the fill character of
your ASCII device. The module removes the colon (:) if you do not select
a character using IW4(10-16).
The module has its own internal fill characters that are not selectable.
When justifying data, the module inserts fill characters according to the
data conversion that you have selected.