Publication 1769-UM009B-EN-P - May 2002
Using the 1769-SDN Scanner Module with CompactLogix Controllers 6-17
To determine how much I/O remains for the scanner module we must
subtract the I/O used by the other I/O modules in the system, along
with the system overhead and end cap detection from the total I/O
supported by the CompactLogix controllers (256 words) as follows:
Calculating Remaining I/O Usage for the Scanner Modules
Now we must calculate the number of actual I/O left in the system for
the scanner. The 1769-SDN scanner is the type of module with both
input and output words.
The amount of I/O words left for the scanner is then calculated as
follows:
8 words + N words = 202, where N = total number of input and
output words for the for the scanner
N = 202 – 8 = 194 words
This means that in the Generic Profile for the 1769-SDN scanner
module, up to a total of 194 words can be used, in any even number
mix, with one limitation:
66 words are needed in the input image for Status information
from the scanner and 2 words are needed in the output image
for the Module Command Array.
This leaves 194 – 68 = 126 words left for actual I/O.
These 66 input words and 2 output words do need to be
included in the total input and output words entered into the
generic profile for the scanner.
Table 6.8 I/O Data used by the 1769-IQ16 and 1769-OV16 Modules
I/O Words Description
256 total I/O words supported by CompactLogix controllers
-30 system overhead
-4 end cap detection
-8 1769-IQ16 total I/O
-12 1769-OV16 total I/O
202 remaining I/O words
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