Rockwell Automation 1746-NI16V SLC 500 Analog Input Modules User Manual - Manual (Page 79)

1 Publication 1746-UM001A-US-P
Chapter
7
Application Examples
Operating Classes This chapter provides two application examples to help you use the
analog input module. They are defined as a:
•
Class 1 example
•
Class 3 example
Class 1
The Class 1 example shows how to configure, read status, and read
data from the NI16 module. Class 1 mode provides 8 words of input
image and 8 words of output image for communicating with the NI16
module. Therefore, this example shows how to multiplex 16 words of
configuration data to the module with 8 output image words by
utilizing a handshaking scheme. Conversely, it also shows how to
read analog data from 16 channels with 8 input image words.
Class 3
The Class 3 example shows how to configure, monitor status, and
read data from the NI16 module. Class 3 mode provides 32 words of
input image and 32 words of output image, making this mode of
operation more desirable. The status for all 16 channels can also be
monitored constantly, while reading data from all 16 channels.
Class 1 Example The following ladder logic program configures all 16 channels of the
1746-NI16 module in Class 1 mode. It then instructs the analog input
module to begin reading data. Class 1 mode should only be used
when the controller is a SLC 500 fixed, SLC-5/01, or when the module
is located in a remote I/O chassis with a 1747-ASB. The significance of
Class 1 mode is that only 8 input words and 8 output words of image
are allowed for exchanging data between the SLC controller and the
NI16 module. This means that configuration data, status, and actual
analog data for the 16 analog channels must be multiplexed using the
8 I/O image words.