Allen-Bradley 1747-SN User Manual page 58

Rung 2:0
To decrease program scan time, copy the first four words of the M1 File
to a binary file and use these addresses throughout the program to access
block transfer done, error, data, etc. information without interrupting
the program scan many times.
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|–––––––––––––––––––––––––––––––––––––––––––––––––+COPY FILE
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Rung 2:1
Examine B3/13 (B3:0/13), an internal storage bit, to determine when a
block transfer is done. Note that examining multiple individual M–file
bits directly (every scan) can measurably increase processor scan time.
| "BT DONE"
| B3
|––––] [––––––––––––––––––––––––––––––––––––––––––+COPY FILE
| 13
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Rung 2:2
Examine B3/12 (an internal storage bit) to determine if a BT error
occurred. Buffer the BT status from B3:3 if an error does occur.
| "BT ERROR"
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| B3
|––––] [––––––––––––––––––––––––––––––––––––––––––+MOVE
| 12
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Rung 2:3
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|–––––––––––––––––––––––––––––––––––––+END+–––––––––––––––––––––––––––––|
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Important:
Scanner Configuration and Programming
If you are using an SLC 5/02 processor M file data
cannot be directly monitored. To monitor M files, you
must move the M file words into an SLC file that can be
monitored, e.g., an integer "N" file. SLC 5/03 or later
processors (running APS 4.02 or later) allow you to
monitor M files directly. However, do not address M
file bits more than necessary throughout your
application program. The processor accesses M files
like immediate I/O. Therefore, excessive addressing of
M files can greatly increase SLC processor scan time.
For more information on M files, refer to appendix B.
+COP––––––––––––––––+ |
+–| |
|Source #M1:1.100| |
|Dest #B3:0| |
|Length
+–––––––––––––––––––+ |
+COP––––––––––––––––+ |
+–| |
|Source #B3:10| |
|Dest #N10:0| |
|Length 64| |
+–––––––––––––––––––+ |
+MOV––––––––––––––––+ |
|Source B3:3| |
| 0000000000000000| |
|Dest N10:64| |
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+–––––––––––––––––––+ |
Publication 1747 6.6 - July 1996
4–13
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