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Memory Allocation

Module Memory Allocation

Module memory allocation highlighting expansion module slots in MapleLogic

When configuring a PLC chassis, certain modules reserve a WORD (16-bits) or a DWORD (32-bits) of X (inputs) and Y (outputs).

Every WORD/DWORD is expressed in Hexadecimal form (0 ~ F (0 ~ 9, A ~ F)).

  • Most modules follow these rules:
PLC-AES0808R and IO-SA0202Y listed in the Card Properties section of the left window in MapleLogic
  • Every CPU is allocated the first DWORD of X and the first DWORD of Y.
    • X0.0 ~ X0.F (1 WORD) and X1.0 ~ X1.F (1 WORD).
      • X0.0 ~ X1.F
    • Y0.0 ~ Y0.F (1 WORD) and Y1.0 ~ Y1.F (1 WORD).
      • Y0.0 ~ Y1.F
    • IMPORTANT: for 16 input/output CPUs, the second half of X and the first half of Y are not used!
      • In ladder logic, X1.0 ~ X1.F and Y0.0 ~ Y0.F are unused.
  • Every other module is allocated AT LEAST one WORD of X and one WORD of Y.
Module memory allocation highlighting expansion module slots in MapleLogic
  • I/O modules with 32 input/output points are allocated one DWORD of X and one DWORD of Y.
Module memory allocation highlighting the IO-SD1616PI and IO-SD0016R expansion modules in MapleLogic
  • <picture>
    • In this example, the IO-SD1616P begins allocation at X4.0 ~ X5.F and Y4.0 ~ Y5.F (DWORD of X and Y). The following expansion module, IO-SD0016R, begins at X6.0 and Y6.0.
      • If an input, button for example, is plugged into the X inputs and an output, light for example, is plugged into the Y outputs, the ladder logic will target the button between X4.0 ~ X5.F.
  • Every module is allocated X and Y, even if it doesn’t use X or Y.
Module memory allocation highlighting IO-SD0016R in MapleLogic
  • <image>
    • In this example, the IO-SD0016R is a relay output-only module. This means there are no inputs to be attached. The Card Properties window will display [_Y:####]. This represents the module only accepting outputs (Y) and no inputs (X).
    • Modules that are input only will display [X_:####], meaning no outputs (Y) are accepted.
  • Unallocated modules display the next WORD for allocation.
Empty slots highlighted in the module memory allocation in MapleLogic
    • If another module is added to the PLC chassis, it is allocated memory starting at X7.0 and Y7.0.

IO-SD0808R

IO-SD0808R highlighted in the module memory allocation within the MapleLogic software

The IO-SD0808R is a special case. The module has 8 digital inputs and 8 relay outputs.

The IO-SD0808R is allocated a WORD of X and a WORD of Y. However, to target the inputs (X) and outputs (Y) of the module, use Xn.0 ~ Xn.7 (first half of the WORD) and Yn.8-Yn.8 (second half of the WORD).

Xn.8 ~ Xn.F and Yn.0 ~ Yn.7 are unused.

n is the module’s reservation slot. Refer below.

Five expansion modules attached to the PLC-AES0808R CPU show in the card properties drop down in the left most window of MapleLogic

Example: In the example image, the IO-SD0808R expansion module begins reservation at WORD 7. To target the inputs (X) and outputs (Y), use X9.0 ~ X9.7 and Y9.8 ~ Y9.F.