User Manual

Rockwell Automation Publication 1756-UM540A-EN-P - May 2014 33
ControlLogix Isolated Analog I/O Module Features Chapter 2
Disabled Keying
Disabled Keying indicates the keying attributes are not considered when
attempting to communicate with a module. Other attributes, such as data size
and format, are considered and must be acceptable before I/O communication is
established. With Disabled keying, I/O communication can occur with a module
other than the type specified in the I/O Configuration tree with unpredictable
results. We generally do not recommend using Disabled keying.
If you use Disabled keying, you must take full responsibility for understanding
whether the module being used can fulfill the functional requirements of the
application.
ATTENTION: Be extremely cautious when using Disabled keying; if used
incorrectly, this option can lead to personal injury or death, property
damage, or economic loss.
EXAMPLE
In the following scenario, Disable keying prevents I/O
communication:
The module configuration is for a 1756-IA16 digital input module. The
physical module is a 1756-IF16 analog input module. In this case,
communication is prevented because the analog module rejects the data
formats that the digital module configuration requests.
Module Configuration
Vendor = Allen-Bradley
Product Type = Digital Input Module
Catalog Number = 1756-IA16
Major Revision = 3
Minor Revision = 1
Physical Module
Vendor = Allen-Bradley
Product Type = Analog Input Module
Catalog Number = 1756-IF16
Major Revision = 3
Minor Revision = 2
Communication is prevented
ANALOG INPUT
ST 0 1 2 3 4 5 6 7
ST 8 9 10 11 12 13 14 15
O
K
CAL
OK
OKFORCE SDRUN
Logix5575
R
U
N
R
E
M
P
R
O
G
DC INPUT
DC INPUT
FLT 8 9101112131415
ST01234567
ST 8 9 10 11 12 13 14 15
O
K
FLT 0 1 2 3 4 5 6 7
DIAGNOSTIC