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Data TypesModbus Term

BCD (Binary Coded Decimal)

A numeric format where each decimal digit is stored in 4 bits within a register.

Definition

BCD (Binary Coded Decimal) encodes each decimal digit as a separate 4-bit nibble. For example, the decimal number 42 is stored as 0x42 — high nibble 4, low nibble 2. A 16-bit register can hold a 4-digit BCD number (0000–9999). BCD is common in older metering equipment and display-oriented devices where the register value looks like the decimal reading.

Quick Facts

Encoding4 bits per decimal digit
Example42 dec → 0x0042 BCD
16-bit range0–9999 (BCD)
Common inOlder meters and counters

Related Terms

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ModPackQT Modbus Glossary · Updated 2026