Rockwell Automation 1771-IJ_IK IK ENCODER/COUNTER MODULES - Manual (Page 29)

4–3 Module/Processor Communication
Publication 1771ĆUM006B-EN-P - June 2002
Bits 00–13 of this word show the accumulated count kept by the
module. This count may be stored either in BCD form, as 000–999
(decimal) or in 12–bit binary form, as a binary value from 0000 0000
0000 to 1111 1111 1111. A switch selection, set during module
installation, determines the numerical form in which the accumulated
count is stored.
Bits 14–17 of this input word serve as status bits. Bit 14, the
diagnostic bit, is set to 1 if the module has detected a fault in its own
operation; normally, this bit is 0. Bits 15 and 16 are the carry and
borrow bits, respectively. These bits indicate whether the count has
overflowed or underflowed.
Bit 17 of the input status word is the home bit. Three conditions are
required to set this bit to 1:
•
Marker input is high
•
Limit switch input is true (high).
•
Home latch enable bit is on (1).
The marker and limit switch input devices connect to module input
terminals. The home latch enable bit is in the control word, one of
the three output words. Note that the home bit, once set to 1,
remains 1 until the home latch enable bit is reset to 0.