Rockwell Automation 1771-ASB/E Remote I/O Adapter User Manual - Manual (Page 44)

3–14 Addressing Modes for Your Remote I/O
Publication 1771-UM001A-US-P - February 2000
Thirty-two-point I/O modules need 32 input or 32 output bits in the
processor’s image table. Because only 16 input and 16 output bits
are available for each I/O group, to address a 32-point I/O module,
the remote I/O adapter module uses the unused input or output word
associated with the adjacent I/O slot.
Refer to Figure 3.12. When the 1771-ASB remote adapter module
addresses a 1-slot I/O group containing a 32-point I/O module, the
adapter module uses the unused word assigned to the adjacent I/O
module slot. For example, the adapter module uses the unused input
word associated with I/O slot 1 (because that slot must hold an
output module and does not use its input word).
Figure 3.13 illustrates the concept of 1-slot addressing with two
32-point I/O modules.
Figure 3.12
1Ćslot I/O Group Concept With 32Ćpoint I/O Modules
32-point I/O M odules
Input W ord 0
O utput W ord 0
Image Table
W ords Allocated
for I/O G roup 0
Input W ord 1
O utput W ord 1
Image Table
W ords Allocated
for I/O G roup 1
Slot 0
Input M odule
I/O G roup 0
Slot 1
O utput M odule
I/O G roup 1
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