Appendix B. User Memory Allocation304 PACSystems* RX7i, RX3i and RSTi-EP CPU Reference Manual GFK-2222ADB-1 Items that Count Against User MemoryThe following items count against the CPU memory and can be used to estimate the minimum amountof memory required for an application. Additional space may be required for items such as AdvancedUser Parameters, zipped source files, user heap, and published symbols.Register Memory Size(%R)Bytes = %R references configured 2Word Memory Size (%W) Bytes = %W references configured 2Analog Inputs (%AI) If point faults enabled: Bytes = %AI references configured 3If point faults disabled: Bytes = %AI references configured 2Analog Outputs (%AQ) If point faults enabled: Bytes = %AQ references configured 3If point faults disabled: Bytes = %AQ references configured 2Discrete Point Faults If point faults enabled: Bytes = 3072Managed Memory(Symbolic Variable and I/OVariable Storage)The total number of bytes required for symbolic and I/O variables. Calculatedas 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/Odiscrete bits is multiplied by 4.Mw = 2 or 3. There are two 8-bit bytes per 16-bit word. If point faults areenabled, the number of bytes is multiplied by 3 because each I/O word requiresan extra byte.EGD (included in HWC) Bytes = 0 if no Ethernet Global Data pages are configuredI/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/Oevery sweep (the default).User Programs Refer to User Program Memory Usage below for details on user programs.
