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Appendix C.
User Memory Size is the number of bytes of memory available to the user for controller
applications.
Items that Count Against User Memory
C.1
The following items count against the CPU memory and can be used to estimate the
minimum amount of memory required for an application. Additional space may be required for
items such as zipped source files, user heap, and published symbols.
Register Memory Size (%R)
Word Memory Size (%W)
Analog Inputs (%AI)
Analog Outputs (%AQ)
Discrete Point Faults
Managed Memory
(Symbolic Variable and I/O
Variable Storage)
I/O Scan Set File
(included in HWC)
User Programs
GFK-2816F
User Memory Allocation
Model
ICRXICTL000
Bytes = %R references configured 2
Bytes = %W references configured 2
If point faults enabled: Bytes = %AI references configured 3
If point faults disabled: Bytes = %AI references configured 2
If point faults enabled: Bytes = %AQ references configured 3
If point faults disabled: Bytes = %AQ references configured 2
If point faults enabled: Bytes = 3072
The total number of bytes required for symbolic and I/O variables. Calculated as
follows:
[(number of symbolic discrete bits) × 3 / (8 bits/byte)]
+ [(number of I/O discrete bits) × Md / (8 bits/byte)]
+ [(number of symbolic words) × (2 bytes/word)]
+ [(number of I/O words) × (Mw bytes/word)]
Md = 3 or 4. The number of bits is multiplied by 3 to keep track of the force, transition,
and value of each bit. If point faults are enabled, the number of I/O discrete bits is
multiplied by 4.
Mw = 2 or 3. There are two 8-bit bytes per 16-bit word. If point faults are enabled, the
number of bytes is multiplied by 3 because each I/O word requires an extra byte.
Based on number of scan sets used.
Note:
32 bytes of user memory are consumed if the application scans all I/O every
sweep (the default).
Refer to User Program Memory Usage below.
Appendix C. User Memory Allocation
User Memory Size
10MB
August 2015
Bytes
10,485,760
307
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