Rockwell Automation 1747-PT1, D1747NP002 Hand-Held Terminal - Manual (Page 457)

Instruction Execution Times
Appendix C
Memory Usage,
C–3
Estimating Total Memory Usage of Your System Using a Fixed or
SLC 5/01 Processor
1. Calculate the total instruction words used by the instructions in your
program and enter the result. Refer to the table on page C–2.
2. Multiply the total number of rungs by .375 and enter the result.
3. Multiply the total number of data words (excluding the
status file and I/O data words) by .25 and enter the result.
4. Add 1 word for each data table file and enter the result.
5. Multiply the highest numbered program file used by 2 and enter
the result.
6. Multiply the total number of I/O data words by .75 and enter the
result.
7. Multiply the total number of I/O slots, used or unused, by .75 and
enter the result.
8. To account for processor overhead, enter 65 if you are using a fixed
controller; enter 67 if you are using a 1747–L511 or 1747–L514.
9. Total steps 1 through 8. This is the estimated total memory usage of
your application system. Remember, this is an estimate, actual
compiled programs may differ by
±
12%.
Total:
10. If you wish to determine the estimated amount of memory remaining
in the processor you have selected, do the following:
If you are using a fixed controller or 1747–L511, subtract the total
from 1024. If you are using a 1747–L514, subtract the total from
4096.
The result of this calculation will be the estimated total memory
remaining in your selected processor.
Important: The calculated memory usage may vary from the
actual compiled program by
±
12%.