Operating Instructions
51
The meter can be ordered with
Option 19K
or
Option 38K
to preconfigure the baud rate to
19.200 or 38,400 baud. See
for details.
ParityMode
(1654)
The WattNode Modbus meter defaults to no parity, eight data bits, and one stop bit, but even
parity is supported using this register, or by ordering
Option EP
to preconfigure even parity
●
0
- N81 (no parity, one stop bit)
●
1
- E81 (even parity, one stop bit)
ModbusMode
(1655)
●
0
- RTU - This is the default Modbus RTU binary protocol
●
1
- TCP-RTU - Emulates the Modbus TCP/IP binary protocol over RS-485
For some applications, it is desirable to convert the RS-485 to TCP/IP over Ethernet. The most
common approaches are the following:
1) Use a Modbus RTU RS-485 to Modbus TCP/IP Ethernet gateway. These devices can trans-
late the RTU packets into Modbus TCP/IP packets and retransmit them over Ethernet. These
work well, but are specialized devices and somewhat expensive.
2) Use an RS-485 to Ethernet serial device adapter. These are less expensive than the Modbus
gateways, but they do not convert protocols from Modbus RTU to Modbus TCP/IP. Most
software designed to receive Modbus over an Ethernet connection will expect the Modbus
TCP/IP protocol. In order to make this work, the meter can switch to the Modbus TCP/IP
protocol (still using RS-485), which is nearly identical to Modbus RTU, but with a different
header and no CRC bytes (TCP/IP has a built-in CRC).
For more information on Modbus over TCP/IP, see “Modbus Messaging on TCP/IP Implementa-
tion Guide - V1.0b”. Implementing a system using Modbus TCP/IP may be complex, so see
http://www.ccontrolsys.com/w/WattNode_Modbus_-_Option_TCP-RTU
and contact Continental
Control Systems for assistance.
The meter can be ordered with
Option TCP‑RTU
to preconfigure the TCP-RTU mode.
ReplyDelay
(1656)
ReplyDelay
configures a user-defined minimum Modbus reply delay between 5 and 180 millisec-
onds (the default is 5 milliseconds). This is useful with some Modbus master devices or software
that can miss response data if the meter responds to a request too quickly.
Diagnostic Registers
SerialNumber
(1701, 1702)
This is a 32 bit long integer register containing the meter’s serial number, as printed on the label.
UptimeSecs
(1703, 1704)
This 32 bit long integer counts the number of seconds the meter has been running since the last
power failure or reset. Resets can be caused by power brownouts or severe errors.
TotalSecs
(1705, 1706)
This 32 bit long integer counts the total seconds of meter operation since factory calibration.
