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Data TypesModbus Term

String Register

ASCII text packed two characters per register across consecutive registers.

Definition

Modbus devices sometimes store text (device names, firmware versions, serial numbers) in consecutive holding or input registers. Two ASCII bytes are packed per 16-bit register. The high byte holds the first character and the low byte the second (in big-endian order), though some devices reverse this. You read the registers with FC03 and interpret each byte as an ASCII character, stopping at a null byte or fixed length.

Quick Facts

Chars per register2 (1 per byte)
Common orderHigh byte = first char
TerminatorNull (0x00) or fixed length

Related Terms

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ModPackQT Modbus Glossary · Updated 2026