ProSoft Technology MVI56-BSAPS - Manual (Page 59)

Reference MVI56-BSAPS ♦ ControlLogix Platform
Bristol Babcock Serial Slave Module
ProSoft Technology, Inc. Page 59 of 83
September 22, 2008
Main Logic Loop
Upon completing the power up configuration process, the module enters an
infinite loop that performs the functions shown in the following diagram.
ControlLogix Processor Not in Run
Whenever the module detects that the processor has gone out of the Run mode
(that is, Fault or PGM), the BSAP ports can be shut down as prescribed in the
user configuration. When the processor is returned to a running state, the module
resumes communications on the network.
Backplane Data Transfer
The MVI56-BSAPS module communicates directly over the ControlLogix
backplane. Data is paged between the module and the ControlLogix processor
across the backplane using the module's input and output images. The update
frequency of the images is determined by the scheduled scan rate defined the
user for the module and the communication load on the module. Typical updates
are in the range of 2 to 10 milliseconds.
This bi-directional transference of data is accomplished by the module filling in
data in the module's input image to send to the processor. Data in the input
image is placed in the controller tags in the processor by the ladder logic. The
input image for the module is set to 250 words. This large data area permits fast
throughput of data between the module and the processor.
The processor inserts data to the module's output image to transfer to the
module. The module's program extracts the data and places it in the module's
internal database. The output image for the module is set to 248 words. This
large data area permits fast throughput of data from the processor to the module.