Publication 1747-RM001G-EN-P - November 2008
C-12 Memory Usage
User Word Comparison
Between SLC 5/03 (and
higher) Processors and the
SLC 5/02 Processor
The SLC 5/03 (and higher) processors and the SLC 5/02 processor
accumulate user words differently during the creation of a user program. The
SLC 5/02 processor is generally more efficient in its word usage than the SLC
5/03 (and higher) processors. However, the SLC 5/02 processor word usage is
difficult to estimate since it is tied to the architecture of the microprocessor.
The SLC 5/03 (and higher) processors accumulates words in a way that is
easier to understand and estimate than the SLC 5/02 processor. The SLC 5/03
(and higher) processors accumulate words similar to a PLC-5.
See page C-1 for user memory capacities for the various SLC processors. It is
important to realize that this does not mean that a 16k, SLC 5/03 processor
can hold a user program that is three times larger than an equivalent SLC 5/02
program. Use the information below to determine the SLC 5/03 user program
size based on existing SLC 5/02 programs.
Instruction Words
Some instructions use the same amount of memory, while other instructions
do not use the same amount of memory. For example, a CTU instruction
always uses 1 word. However, an ADD instruction in an SLC 5/02 processor
uses 1.5 words; in a SLC 5/03 (or higher) processor an ADD instruction uses
3 words. Also note additional differences below:
Exact program content determines the program size difference. An SLC 5/03
program consumes 20% to 150% more instruction words than its SLC 5/02
equivalent.
Table C.4 Memory Usage
Condition SLC 5/02 Words SLC 5/03 Words SLC 5/04 and
SLC 5/05 Words
Each rung 0.375 1 1
Each additional Program File 1 5 5
Each additional Data File 1 5 5
Each I/O Slot 0.75 3 3
Overhead 216 236 250
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