Appendix B. User Memory Allocation
304 PACSystems* RX7i, RX3i and RSTi-EP CPU Reference Manual GFK-2222AD
B-1 Items that Count Against User Memory
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 Advanced
User Parameters, zipped source files, user heap, and published symbols.
Register Memory Size
(%R)
Bytes = %R references configured ï‚´ 2
Bytes = %W references configured ï‚´ 2
If point faults enabled: Bytes = %AI references configured ï‚´ 3
If point faults disabled: Bytes = %AI references configured ï‚´ 2
If point faults enabled: Bytes = %AQ references configured ï‚´ 3
If point faults disabled: Bytes = %AQ references configured ï‚´ 2
If point faults enabled: Bytes = 3072
Managed Memory
(Symbolic Variable and I/O
Variable Storage)
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.
Bytes = 0 if no Ethernet Global Data pages are configured
I/O Scan Set File
(included in HWC)
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 for details on user programs.
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