Rockwell Automation 1771-IS 5V DC INPUT MOD - Manual (Page 21)

Programming and Operation
Chapter 3
3-2
4-digit Thumbwheel Switch Data (16-bit storage)
Data is loaded into memory based on whether you have selected the
maintained or momentary switch contact mode (SWITCH #4).
Maintained Contact Mode
When 4-digit BCD thumbwheel switches are wired according to the block
diagram in Figure 3.2a, the switch settings will be stored automatically in
the data table after a block transfer as shown in Figure 3.2b. The first
word is reserved for diagnostic data. Each remaining word stores the four
digits of the thumbwheel setting. The digits MSD, UMD, LMD and LSD
have been loaded, respectively, from left to right, in the same order that
they are normally read (left to right). For example, observe how the
4-digit switch setting 9753 of thumbwheel switch #2 is loaded into the
data table.