The basic data processing units used in ladder logic are Word (16-bit) and Double Word (32-bit). In the CUBLOC ladder environment, strict numerical ranges must be observed to prevent interference with system-reserved addresses.

• D-Area (Data Register): Basically composed of 16-bit (1 Word) units.
• Double Word Processing: To handle 32-bit data, two consecutive D-areas are required (e.g., combining D0 and D1 to store a single 32-bit value).

This system operates on the principle of using Unsigned Integers to prevent data collisions with hardware control ports (P, WP, etc.).

Critical Notice: Both Word and Double Word (D-Word) should be processed as Unsigned (Positive). In particular, Double Words must be used within the upper limit of 0x7FFEFFFF to avoid encroaching on the system-reserved address area (0x7FFF1000 and above).

• The area from 0x7FFF1000 to 0x7FFFFFFF is reserved for Memory-Mapped I/O addresses to control hardware I/O ports (P0, WP0, etc.).
• Prohibition of Negative Numbers (2's Complement): If the Most Significant Bit (MSB) is set to 1 to represent a negative number (e.g., 0x80000000 or higher), the system may misinterpret it as a system-reserved address rather than a number, causing calculation errors or hardware malfunctions.
• Recommendation: If negative arithmetic is required, do not use signed values directly. Instead, manage a separate D-area as a sign flag (e.g., 0: Positive, 1: Negative) within your logic.

• If a calculation result exceeds 2,147,418,111 (0x7FFEFFFF), it overlaps with internal system addresses, resulting in data corruption.
• You must implement logic to filter or cap values before they exceed this upper limit during input or arithmetic processes.

Entering a value that exceeds the system limit into a Double Word (e.g., 0xEE6B4000) will result in an error or incorrect calculation results, as shown below:

Always ensure you use positive values below the upper limit:

While it is technically possible to input negative numbers using DWMOV, this should be avoided as it can trigger unpredictable system errors:

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