BMS Logic Academy - Modbus Toolkit

Important: Some BMS/gateway software uses zero-based Decimal/JBus addressing, while some manufacturers show traditional Modbus/Modicon 3xxxx/4xxxx notation. Always confirm which addressing format your software expects before engineering the point.

Enter a register value, select the address format used by the manufacturer’s register list, then select the Modbus function code.

Register Input

Register Value

Input Type

Function

Calculated Outputs

Decimal / JBus Address6

Hex Address0006

Modbus / Modicon Address40007

Quick Examples

Input	Input Type	Function	Output
0006	Hex	03 - Holding Register	Decimal 6 / Modbus 40007
6	Decimal / JBus	03 - Holding Register	Hex 0006 / Modbus 40007
40007	Modbus / Modicon	03 - Holding Register	Decimal 6 / Hex 0006
0014	Hex	03 - Holding Register	Decimal 20 / Modbus 40021

Addressing Reminder

Traditional Modbus notation is normally 1-based and includes a function prefix. For example, Holding Register 40007 is decimal/JBus address 6 because 40007 - 40001 = 6.

Template Notes

This decoder does not confirm byte order, scaling, signed/unsigned format or whether the point exists in the device. Always verify against live readings and the manufacturer register list.

Important: A Modbus 16-bit register contains 16 individual bits. Each bit can represent a separate status/fault/alarm condition, or all 16 bits can be combined to form a numeric signed or unsigned integer value.

Enter a 16-bit register value, select whether it should be treated as unsigned or signed, and the tool will display the individual bit states from Bit 15 down to Bit 0.

Register Value

Value Type

Calculated Outputs

Converted Unsigned25

Signed Equivalent25

Hex0019

High Byte0 / 00

Low Byte25 / 19

Decoded Bit Status

Addressing / Bit Number Reminder

Bit 15 is the most significant bit (MSB), and Bit 0 is the least significant bit (LSB). Many manufacturers list bits in the order 15..0, but some list 0..15, so always confirm the register list convention.

Template Notes

Use this sheet when a Modbus register contains packed status bits, fault codes or alarm flags. This tool decodes the 16 bits within a single Modbus register. It does not resolve 32-bit word order or byte order issues between two registers.

Important: This tool works in the opposite direction to Value to Bits. Set each bit to 0 or 1 and the tool calculates the resulting 16-bit register value.

Enter individual bit states as 0 or 1. The tool will calculate the resulting unsigned value, signed two’s-complement value, hexadecimal value, high byte and low byte.

Bit States

Calculated Outputs

Unsigned Total0

Signed Total0

Hex0000

High Byte0 / 00

Low Byte0 / 00

Bit Weight Reference

Two’s Complement Reminder

If the unsigned total is greater than 32767, the signed 16-bit equivalent is calculated as unsigned total - 65536.

Template Notes

This is useful when a manufacturer gives individual bit meanings and you need to understand the decimal value that would be seen if multiple bits were active at the same time.