Rockwell Automation 1747-DCM,D17476.8 Direct Communication Module - Manual (Page 27)

Chapter 3
Addressing
3–3
SLC Addresses
The three parts of the SLC address include the:
•
physical slot
•
word
•
bit
I = Input
O:1.7/8 I:2.3/8
2 = Physical Slot
3 = Word
8 = Bit (decimal)
O = Output
1 = Physical Slot
7 = Word
8 = Bit (decimal)
SLC Input Address SLC Output Address
The slot address refers to the physical slot (1–30) in the modular SLC chassis
or fixed SLC expansion chassis where the DCM is installed. This address
does not need to match the logical rack address of the PLC I/O instruction.
The word address refers to the word number (0–7) of the slot being
addressed. The maximum number of SLC I/O words that a DCM can be
assigned is 8.
The bit address is the bit within the word being addressed. Bits are
numbered 0–15 (decimal) for the SLC and 0–17 (octal) for the PLC. Outputs
from the SLC output image are inputs to the supervisory processor input
image table. Likewise, outputs from the supervisory processor output image
table are inputs to the SLC image table.
As noted, if the supervisory processor is a PLC the I/O image bits are octal
and SLC bits are decimal. While the addresses are different, the position of
the bit in the SLC word must match the position of the bit in the PLC word.
The following diagrams show this relationship.