Publication 1769-UM009B-EN-P - May 2002
Using the 1769-SDN Scanner Module with CompactLogix Controllers        6-15
You may add your own logic to the program and wire some I/O to 
test the I/O in the 1769-ADN adapter, or you may simply turn on 
outputs in the scanner’s output tags in the controller to verify that they 
physically turn on at the output card. In addition, you may wire an 
analog output to an analog input to verify the operation of the 
network and the analog modules. Be sure the analog modules are 
properly configured for such operation.
When your program is written, verify and save it, then download it 
to your controller to run and test your system.
Calculating Maximum I/O 
Sizes for the 1769-SDN 
Scanner Module
The calculations in this section apply to all Series A CompactLogix 
controllers, firmware revision 10 and earlier.
The amount of I/O a CompactLogix version 8 controller can exchange 
with Compact I/O modules is 256 16-bit words. In addition to the I/O 
words, the following items must be accounted for in the calculations:
• 4 words must be allotted for end cap checking
• 30 words must be allowed for system overhead requirements
There are two types of I/O modules in a CompactLogix system:
• Modules with only input data
• Modules with both input and output data
Modules with only input data are typically discrete input modules like 
the 1769-IQ16 and 1769-IA16. Discrete output modules, analog 
modules, and specialty modules contain both input and output 
images.
TIP
If any module in a CompactLogix system 
requires more than 30 words for its 
configuration file, then that length should be 
used for the system overhead value.
Allen-Bradley Drives