Allen-Bradley 1794-IT8, User Manual

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5–7 How Communication Takes Place and I/O Image Table Mapping with the DeviceNet Adapter
Publication 1794-6.5.7 – April 1997
Each I/O module has default values associated with it. At default,
each module will generate inputs/status and expect
outputs/configuration.
Module Defaults for: Factory Defaults Real Time Size
Catalog
Number
Description
Input
Default
Output
Default
Input
Default
Output
Default
1794-IT8 8 Thermocouple Input 11 4 10 0
Factory defaults are the values assigned by the adapter when you:
•
first power up the system, and
•
no previous stored settings have been applied.
For analog modules, the defaults reflect the actual number of input
words/output words. For example, for the 8 thermocouple input
analog module, you have 11 input words, and 4 output words.
You can change the I/O data size for a module by reducing the
number of words mapped into the adapter module, as shown in “real
time sizes.”
Real time sizes are the settings that provide optimal real time data to
the adapter module.
Analog modules have 15 words assigned to them. This is divided
into input words/output words. You can reduce the I/O data size to
fewer words to increase data transfer over the backplane. For
example, an 8 thermocouple input module has 11 words input/4
words output with factory default. You can reduce the write words to
0, thus eliminating the configuration setting and unused words. And
you can reduce the read words to 10 by eliminating the calibration
status words.
For information on using DeviceNetManager software to configure
your adapter, refer to the DeviceNetManager Software User Manual,
publication 1787-6.5.3.
More
Defaults