Modular Power Meter
Modular power meter version 1.0 Page 15 / 40
6. Modbus Interface
6.1.
Modbus Settings
The modbus address and baudrate can be set by the user.
The available baud rates are 4800, 9600, 19600, 38400, 57600 and 115200. The
communication uses 8 data bits without parity and 1 stop bit. It is in binary format with most
significant digits first and 16-bit CRC
Internally the receiver channel is doubled, while the first channel is used for the MODBUS
communication at the selected baud rate, the second channel is fixed to 9600bd so a user
can always communicate at 9600bd to configure the module.
The settings can be changed in several ways:
- via a ModbusLink PC program (see chapter 7);
- via the display with touch interface (Volt1000 only);
- via modbus on a fixed 9600 baudrate.
- via modbus on the (previously) configured baudrate
6.2.
Modbus address
When used in a chain configuration, the first sensor on the bus takes its stored address and
all connected Cube1000AN/RoCo2000AN meters get the address of the first sensor + 1..15
by default. The number 1..15 is the sensor position after the first sensor. Care must be taken
that this does not overlap with the addresses of other modules on the bus!
A MODBUS bus termination resistor of 120Ω is fixed in the Volt1000/Cube1000/RoCo2000AN
module. So this sensor is always the last element in the MODBUS-RTU
The first sensor is the only one that is directly connected to the modbus. It acts as a router
for the chained Cube1000AN/RoCo2000AN meters so all meters can be reached from the
modbus.
Example
A Volt1000 meter with address 10 has 3 Cube1000/RoCo2000 meters attached to it.
The bus addresses are:
- Volt1000: 10
- first Cube1000/RoCo2000: 11
- second Cube1000/RoCo2000: 12
- third Cube1000/RoCo2000: 13
6.3.
Modbus Registers
6.3.1. Number formats
Number coding:
- 32-bit number (int32): The MSB always comes first, or register n contains bit 31..16
and register n+1 contains bit 15..0
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