Rockwell Automation 1771-DA,D17716.5.13 U MNL 1771-DA ASCII I/O MODULE - Manual (Page 61)

Choosing Module Features
Chapter 3
3Ć19
Table 2.J
String Length
If Your ASCII Device
You Determine Maximum
String Length By
Automatically places the endĆofĆstring delimiter to separate
data such as bar codes
Setting the module's string length to
the (longest) length that the ASCII
device can transmit (module in data
mode)
Is a data terminal Setting the string length to the
longest message or line, and
entering the endĆofĆstring delimiter
at the end of each message or line
(report generation mode)
You will use the string length to determine the block length of the read
block transfer instruction and the size of the data table file that receives
the string. Refer to section titled Determining Block Transfer Length,
P. 2-20, and to section titled Choosing Single or Multiple Transfers
IW2(17) P. 2-25 for additional information.
If the string length from the ASCII device exceeds the string length that
you set for the module, the next character (beyond the set string length)
received in the module’s input buffer causes the module to transfer the
string. That character and any additional characters remain in the input
buffer until the next transfer.
Set the string length equal to the longest string of characters that your
ASCII device can generate in your application. Record the string length
in IW2(11-13) by writing the BCD value of the string length using the
form (found at the end of this chapter) or the boxes below.
13 12 IW2
ASCII Characters/String
11 10 07 06 05 04 03 02 01 00