Rockwell Automation 1771-DA,D17716.5.13 U MNL 1771-DA ASCII I/O MODULE - Manual (Page 126)

ASCII I/O Module Tutorial
Chapter 4
4Ć52
When in data mode, select a data conversion type compatible with the
characters transmitted by your ASCII device. Your selection is limited to
one of the following conversion types:
Conversion Type Data Characters
2 ASCII characters per word
1 ASCII character per word
3 BCD characters per word
4 BCD characters per word
4 hex characters per word
ASCII standard code
0 thru 9
0 thru 9, A thru F
When operating in report generation mode, the module selects two ASCII
characters per word for message characters. You choose the data
conversion for message variables (BCD values) placed between
delimiters. Your selection is limited to one of the following:
Conversion Type Data Characters
3 BCD characters per word
4 BCD characters per word
0 thru 9
How Binary and BCD Differ
The PLC-3 manipulates message variables such as timer/counter preset
and accumulated values in signed binary (sign in bit 16). If your program
does not convert message variables to BCD, the module will display
erroneous values because the binary and BCD bit patterns of a value are
different. For example, compare how the bit pattern 10110 would be
interpreted in binary and in BCD (Figure 3.10).
Demonstrating Data Conversion