32-bit registers “Enron Modbus” allows larger registers where you can store 32 bits in a single register So you can read and write like normal (but with values limited to the range 0-255).

The data is nevertherless transmitted as 16 bit over the serial link, 8-bit registers For example Danfoss use 8-bit registers for storage of some settings internally Unicode/UTF-8 is typically not supported. Often 16 consecutive registers are used, allowing 32 characters in the string. Strings Each register (16 bits) is interpreted as two ASCII characters (each 1 byte = 8 bits). Unfortunately the byte order might differ between manufacturers of Modbus instruments. How to convert from the bit values to the floating point value is described in Floats (single or double precision) Single precision floating point values (binar圓2) are defined by 32 bits (4 bytes),Īnd are implemented as two consecutive 16-bit registers.Ĭorrespondingly, double precision floating point values (binary64) useĦ4 bits (8 bytes) and are implemented as four consecutive 16-bit registers. The byte order might differ between manufacturers of Modbus instruments. Negative values can be stored if the instrument is defined that way, and is The range is 0 to 4294967295, which is called ‘unsigned INT32’. Long integers (‘Unsigned INT32’ or ‘INT32’) These require 32 bits, and are implemented as two consecutive 16-bit registers. Help functions to calculate the two’s complement value (and back) are Interpreted as negative value (in the range -32768 to -1). Implemented as any received value in the upper range (32768-65535) is Instead of anĪllowed integer range 0-65535, a range -32768 to 32767 is allowed. Negative numbers (INT16 = short) Some manufacturers allow negative values for some registers. Some extensions not covered by the official standard ¶ Scaling of register values Some manufacturers store a temperature value of 77.0 C as 770 in the register, Note that function code 23 not is implemented by this software (it is forįunction codes 128 and larger are used by slaves to indicate errors. Read-and-write registers (holding registers) Several digital outputs, or a setting parameterįunction codes are used to describe the read or write operations (shown in decimal in the table below) Storage Several digital inputs, or an analog input Or in a 16-bit register, and whether it is possible to write to the storage. Modbus defines “table” names dependent on whether the storage is in a single bit Range 0 to 65535 (dec), which is 0 to ffff (hex).

Modbus command format