Rockwell Automation 1771-DB Basic Module User Manual - Series A - Manual (Page 147)

Data Types
Chapter 7
7–5
This value requires two words of the processor data table. The first word
contains the overflow, underflow, sign data and the three most significant
digits of the value. The second word contains the lower three digits of the
value (figure 7.6). The value ranges from -999.999 to +999.999. If an
overflow or underflow condition exists, a value of 000.000 is reported and
the appropriate bit is set. Any digits more than 3 places to the right of the
decimal point are truncated.
Figure 7.6
Truncated 3.3-Digit BCD
7.2.6
3.3-digit, Signed,
Fixed Decimal BCD