Modbus Registers
Table of Standard Dataset Common Registers
The main information needed for remote supervision of a ComPact NSX, ComPact NS, MasterPact NT/NW or MasterPact MTZ circuit breaker is contained in the table of common registers starting at register 32000.
One Modbus read request is limited to 125 registers maximum. Three Modbus read requests are necessary to read the entire table.
It contains the following information:

Circuit breaker status

Tripping causes

Realtime values of main measurements: current, voltage, power, and energy
The content of this table of registers is detailed in Standard Dataset Common Registers.
Use of these common registers is highly recommended to optimize response times and simplify the use of data.
Table Format
Register tables have the following columns:
Address 
Register 
RW 
Unit 
Type 
Range 
A/E 
A/E/P/H 
X 
Description 


Address: a 16bit register address in hexadecimal. The address is the data used in the Modbus frame.

Register: a 16bit register number in decimal (register = address + 1).

RW: register readwrite status

R: the register can be read by using Modbus functions

W: the register can be written by using Modbus functions

RW: the register can be read and written by using Modbus functions

RC: the register can be read by using the command interface

WC: the register can be written by using the command interface


Unit: the unit the information is expressed in.

Type: the encoding data type (see data type description below).

Range: the permitted values for this variable, usually a subset of what the format allows.

A/E: types of ComPact NSXMicroLogic trip unit for which the register is available.

Type A (Ammeter): current measurements

Type E (Energy): current, voltage, power, and energy measurements


A/E/P/H: types of MasterPact NT/NW and ComPact NSMicroLogic trip unit for which the register is available.

Type A (Ammeter): current measurements

Type E (Energy): current, voltage, power, and energy measurements

Type P (Power): current, voltage, power, energy measurements, and advanced protection

Type H (Harmonics): current, voltage, power, energy, energy quality measurements, and advanced protection


X: register available in the MicroLogic X control unit for MasterPact MTZ circuit breakers.

Description: provides information about the register and restrictions that apply.
Data Types
Data Types 
Description 
Range 

INT16U 
16bit unsigned integer 
0 to 65535 
INT64 
64bit signed integer 
 9 223 372 036 854 775 808 to + 9 223 372 036 854 775 807 
INT64U 
64bit unsigned integer 
0 to 18 446 744 073 709 600 000 
FLOAT32 
32bit signed integer with a floating point 
2^{126} (1.0) to 2^{127} (2  2^{23}) 
BigEndian Format
INT64 and INT64U variables are stored in bigendian format: the most significant register is transmitted first and the least significant register is transmitted at last place.
INT64 and INT64U variables are made of INT16U variables.
The formulas to calculate the decimal value of these variables are:

INT64: (0bit63)x2^{63} + bit62x2^{62} + bit61x2^{61} + ...bit1x2^{1} + bit0x2^{0}

INT64U: bit63x2^{63} + bit62x2^{62} + bit61x2^{61} + ...bit1x2^{1} + bit0x2^{0}
Example:
The total active energy in the standard dataset is an INT64 variable coded in registers 32096 to 32099.
If the values in the registers are:

register 32096 = 0

register 32097 = 0

register 32098 = 70 (0x0046) 0x0017 or 23

register 32099 = 2105 (0x0839) 0x9692 or 38546 as INT16U variable and 26990 as INT16 variable (use the INT16U value to calculate the value of the total active energy).
Then the total active energy is equal to 0x2^{48} + 0x2^{32} + 23x2^{16} + 38546x2^{0} = 1545874 Wh.
Data Type: FLOAT32
Data type FLOAT32 is represented in the single precision IEEE 754 (IEEE standard for floatingpoint arithmetic). A value N is calculated as indicated below:
N = (1)^{S} x 2^{E127} x (1+M)
Coefficient 
Stands for 
Description 
Number of Bits 

S 
Sign 
Defines the sign of the value: 0 = positive 1 = negative 
1 bit 
E 
Exponent 
Excess 127 binary integer added. When 0 < E < 255, the actual exponent is: e = E  127. 
8 bits 
M 
Mantissa 
Magnitude, normalized binary significant 
23 bits 
Example:
0 = 0 00000000 00000000000000000000000
1.5 = 1 01111111 10000000000000000000000
with:

S = 1

E = 01111111 = 127

M = 10000000000000000000000 = 1x2^{1} + 0x2^{2} +...+ 0x2^{23} = 0.5

N = (1) x 2^{0} x (1+0.5) = 1.5
Quality of Bits in Registers
The quality of each bit of a register coded as INT16U data type as an enumeration of bits can be indicated in the register preceding the register.
Example:
The quality of each bit of the register 32001, circuit breaker status, is given in the preceding register, 32000.
The quality of the data corresponding to the bit 0 of register 32001, OF status indication contact, is given in the bit 0 of register 32000:

bit 0 of register 32000 = quality of OF status indication

bit 0 of register 32001 = OF status indication contact
If 
Then 

If bit 0 of register 32000 = 1 AND bit 0 of register 32001 = 0 
The OF contact indicates that the device is open 
If bit 0 of register 32000 = 1 AND bit 0 of register 32001 = 1 
The OF contact indicates that the device is closed 
If bit 0 of register 32000 = 0 
The OF contact indication is invalid 