16
2. Write the Read-File request with the section number and channel ID as shown in the
previous step.
3. Read the record data from the file response block.
4. Write an acknowledgment for the file. The file section pointer will be moved to the next
record.
5. Repeat steps 3-4 until all the section records are read.
Reading Real-time Waveforms
Writing the Read-File request for file 128 provides a simultaneous capture of 6 real-time
waveform records – three voltage and three current waveforms – into a communication
buffer that can be read through the common file response block. The following gives a
summary of steps for reading real-time waveforms:
1. Write the Read-File request for file 128. Address you request to the first file section (its
number is always zero), or to the first file channel (if you know channel’s ID). If you use
a channel ID, preset the section number field to 0xFFFF.
2. Read the channel’s data from the file response block.
3. Write the Read-File request for the next file section or channel. The file response block
will be refilled with the data for the requested channel.
4. Repeat steps 3, 4 until all the channel records are read.
5. Write an acknowledgment to release the buffer.
2.11 TCP Notification Client
The TCP notification client can establish connections with a remote Modbus/TCP server and
send notification messages either on events, or periodically on a time basis.
Notification messages are sent via a block of 16 Modbus registers using write function 16.
The following table shows the message exchange structure.
Modbus
Register
Description Type
Comment
+0-1 Device serial number
UINT32
+2-4 Device MAC address
CHAR6
+5 Device address
UINT16
Device port address
+6-7 Device IP address
UINT32
Network byte order
+8 Event type
UINT16
See F22 in Section 5
+9 Event sequence number
UINT16
Not used
+10-11 Event timestamp, seconds
UINT32
Local time since Jan 1, 1970
+12-13 Event timestamp, seconds fraction, in microseconds
UINT32
+14-15 Reserved
UINT32
Written as 0
After receiving a write acknowledgement from a server, a TCP connection is still open for 10
seconds (20 seconds via GPRS) to give the server an opportunity to access meter registers
through an open socket. It may help you access the meter from outside your local
network when the server is located on another network, or when using wireless GPRS
communications. The notification client will respond to all server requests as if it were a
regular incoming connection.
If the server does not close a connection, it will be closed in 20 seconds if there is no
activity on the socket. In the event a connection attempt was unsuccessful, the notification
client retries two more times before announcing a connection failure.
The server’s IP address, port number and starting Modbus register address are
programmable in the meter. See “TCP Notification Client Setup” for more information on the
client setup. To configure and enable the notification client in your meter via PAS, select
Communication Setup in the Meter Setup menu, and click on the TCP Notification Client
Setup tab.
Provided
by
Northeast
Power
Systems,
Inc.
www.nepsi.com
