Slc And Scanner Asynchronous Operation - Allen-Bradley 1747-SN User Manual

SLC Processor Scan Cycle
The SLC processor reads the
scanner input image file into the
SLC input image file, processes
it, and creates an SLC output
image file. The SLC processor
transfers its output file to the
scanner.
Important: The outputs of the RIO are updated after the end of the first SLC processor scan.

SLC and Scanner Asynchronous Operation

The SLC processor scan and RIO scanner scan are independent
(asynchronous) of each other. The SLC processor reads the scanner
input image file during its input scan and writes the output image file
to the scanner during its output scan. The RIO scanner continues
reading inputs and writing outputs to the scanner I/O image file,
independent of the SLC processor scan cycle.
Depending on your SLC processor, RIO link configuration, and
application program size, the scanner may complete multiple scans
before the SLC processor reads the scanner's input image file. The
RIO scanner updates its I/O files on a per logical rack basis.
The figure below illustrates the asynchronous operation of the SLC
processor and RIO scanner.
SLC Input
Image File
Program
SLC Output
SLC Processor
Image File
Output Input
Scanner
Image Image
Input
Device 3 Device 1
Image File
Input
Image
Device 3
Output
Image
Device 2
Scanner Output
Image File
Overview
RIO Scanner Scan Cycle
The scanner updates its
input image file each time
Output
it scans a logical device.
Image
The scanner may scan all
Device 1
of its configured logical
devices several times
before the SLC processor
Input
reads the scanner's input
Image
image file.
Device 2
Publication 1747 6.6 - July 1996
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