This page explains the differences between P, M, D, C, T, and R memory, address notation, memory-region settings, the Used Memory Map, and time-driven special contacts.

About screenshots: Screenshots use the Korean user interface. Button positions, icons, and keyboard shortcuts are the same.

Memory holds input states, internal conditions, calculation results, timer values, and other data while the program runs. Ladder logic and Arduino C code in MPINO Studio 2 can share and use this memory.

A basic address consists of a region letter followed by a zero-based number. For example, M10 is the eleventh address in the M region, and D0 is the first address in the D region.

P address caution: P addresses can be reviewed and changed in Board Pin Editing. Their I/O directions and physical terminals follow the definition of the board selected for the project.

R value error caution: Because of the limits of 32-bit floating-point arithmetic, 0.1 + 0.2 may be stored as approximately 0.30000001 instead of exactly 0.3. This characteristic must be considered on controllers that use IEEE 754 32-bit floating point.

The MPINO-8A4R(T)-S board uses these default memory counts:

You can change the number of addresses used under Settings → Memory Region Settings.

Memory Region Settings: Blank P, M, D, C, T, and R fields use the board defaults. Entering a value changes the count for that project. The bottom of the dialog shows estimated SRAM use together with total SRAM.

Do not confuse a count with the last address. Numbering begins at zero, so 200 D addresses run from D0 through D199.

On MPINO-8A4R(T)-S, analog inputs, NTC temperature inputs, and PWM are connected to C0 through C10 memory.

You can change the mapped memory under Settings → Ladder Pin Map Settings.

Analog/PWM output caution: When memory is mapped to an analog or PWM output, the value at the mapped address drives that output. You therefore cannot use analogWrite-related functions for the same output in Arduino code. To use an analogWrite-related function, clear Use for that output under Settings → Ladder Pin Map Settings.

Critical check: If you choose C0 through C10 as ordinary counter addresses on this board, their data can overlap with the board functions that use the same addresses. Before assigning a counter, inspect both the pin map under Board/Memory Information and the Used Memory Map.

Mapped addresses vary by board and can also be changed by the user. Check them under Settings → Ladder Pin Map Settings.

Data width is the number of bits read or stored at one time. It determines the available value range and memory use.

The R region also uses 32 bits, but it stores a floating-point value, not a DWORD integer. Do not treat R memory as DWORD access simply because both use 32 bits.

When selecting a width, consider the largest value after calculations. A value incremented every 1 ms for one day reaches 86,400,000 and therefore exceeds the WORD range.

Read a long address from left to right as a data-width prefix, memory region, address index, and bit number.

For example, WM1.3 means:

1. W: view the data with WORD width.
2. M: use the internal-bit memory region.
3. 1: the WORD address. It identifies the second WORD group, after WM0.
4. .3: select the fourth bit in that WORD. Bit numbering also begins at zero.

This diagram shows the memory structure for bits, bytes, words, double words, and floating-point values.

The P and M regions group individual BIT addresses in sets of 8, 16, or 32 for BYTE, WORD, and DWORD views. The lowest address is the least significant bit, so WM0.0 refers to M0, and WM1.3 refers to M19.

Each D, C, or T address is one WORD. Two consecutive WORDs form a DWORD: DD0 combines D0 and D1, while DD1 combines D2 and D3. C and T use the same rule through forms such as DC0 and DT0.

Select Settings → Memory Region Settings, or press Ctrl+Shift+M.

Check the dialog in this order:

1. Confirm that the current project board is MPINO-8A4R(T)-S.
2. Review the counts in the P, M, D, C, T, and R fields.
3. A field left blank uses the selected board's default value.
4. Review the estimated SRAM use and total SRAM at the bottom.
5. If the total is exceeded, the indicator turns red and the settings cannot be saved.
6. If a change is required, enter the value and select Save.
7. Close the dialog and press Ctrl+S to store the change in the .mp2 project.

Keep the board defaults unless the project has a clear reason to change them. Increasing a count provides more addresses but consumes more SRAM. Reducing a count can leave an existing ladder cell or Arduino C reference outside the valid range, so inspect the Used Memory Map before and after the change.

Select View → Used Memory Map, or press Ctrl+Shift+L.

Use the map as follows:

1. Select the P, M, D, C, T, or R tab.
2. Narrow the results with the ladder and code source filters.
3. Enter an address in the search field and press Enter.
4. A colored address cell means that the current project uses that memory.
5. Select a used cell to display its references below the grid.
6. Select a reference to jump to the ladder cell or code location.
7. The selected tab and scroll position remain when the dialog is reopened. They reset when the application restarts.

1. Open the project saved in Phase 1.
2. Press Ctrl+Shift+L.
3. Select the P tab.
4. Confirm that P0 and P32 are marked as used.
5. Select P0 and confirm the NO contact reference in ladderLoop.
6. Select P32 and confirm the output-coil reference.

Inspecting this map before reassigning an address or reducing a memory-region size helps prevent duplicate use and out-of-range references.

A special contact beginning with @ is updated automatically as time passes. It is different from an ordinary P or M memory address.

@100 still produces one ON scan when the program scan crosses a 100 ms boundary without landing exactly on it. It can start an operation or increment a value at regular intervals.

@F1000 provides a repeating one-second condition without code that manually toggles a state.

Follow these input rules:

• The time unit is milliseconds (ms).
• Do not use parentheses. Enter @F1000, not @F(1000).
• Use a special contact only in a contact or rising/falling-edge cell.
• Do not enter it as an output-coil address.
• An arbitrary name such as @ON is not valid.

Replace the P0 contact in the Phase 1 circuit with an @F1000 special contact.

1. Open the Phase 1 project and use File → Save As to save phase2-memory.mp2.
2. Confirm that output loads are disconnected.
3. Select the P0 contact cell in ladderLoop.
4. Press Enter or double-click to open the cell editor.
5. Change the address to @F1000 and confirm it.
6. Keep P32 as the output-coil address.
7. Press Ctrl+R and confirm that the build finishes successfully.
8. Connect the MP download cable and select the port at the lower right.
9. Press Ctrl+U to upload.
10. If you configured a monitoring port in Phase 1, press Ctrl+M to enable real-time ladder monitoring.
11. Confirm that the @F1000 contact and P32 coil repeat approximately 1 second ON and 1 second OFF.

To resume the physical-input test afterward, restore the contact address to P0, then build and upload again.

You have completed Phase 2 when you can explain or verify every item below.

• Distinguish the purposes of P, M, D, C, T, and R.
• Explain that C0 through C10 are mapped to board functions on MPINO-8A4R(T)-S.
• Identify the size and signed range of BIT, BYTE, WORD, and DWORD.
• Read WM1.3 and DD2 by the role of each character.
• Open Memory Region Settings with Ctrl+Shift+M.
• Find the P0 and P32 references with Ctrl+Shift+L.
• Explain the difference between @100 and @F1000.
• Save the exercise as a separate project and verify the build result.

• Phase 1 · Create Your First Project
• MPINO STUDIO 2 User Manual

← Phase 1 · Create Your First Project | Back to the MPINO STUDIO 2 User Manual