Chapter 1 Communications; Communication Procedures; Communication Timing - Panasonic KW9M User Manual

Chapter 1 Communications

1.1 Communication Procedures

Communication starts with command transmission from the host computer (hereafter Master) and ends
with the response of Eco-POWER METER (hereafter Slave).
Master Slave
Comin,and
Data
Comin,and
Acknowledgement
Comin,and
Negative
acknowledgement
Comin,and
No response

1.2 Communication timing

◆The minimum access time from the master is 1 sec. (Minimum time for update the data)
Eco-POWER METER may not response due to noise and so on, be sure to check that it receives the
response from Eco-POWER METER.
◆In order to improve the communication quality, we recommend to send the transmission again.
Communication timing of RS485
◇Eco-POWER METER (Slave) side
When Eco-POWER METER (Slave) starts transmission to RS485 communication line, it is arranged
so as to provide an idle status transmission period of about 1 to 99ms (setting available) before
sending the response to ensure the synchronization on the receiving side. After sending the response,
master can disconnect the transmitter from the communication line within transmission period 20ms.
◇Master side (Cautions of setting a program)
At communication, keep the following conditions.
1) Set the program so that the master can disconnect the transmitter from the communication line
within the transmission period of about 20ms after sending the command in preparation for
reception of the response from Eco-POWER METER (Slave).
2) To avoid collision of transmissions between the master and Eco-POWER METER (Slave), send a
next command after checking that the master received the response.
Phone: 800.894.0412 - Fax: 888.723.4773 - Web: www.clrwtr.com - Email: info@clrwtr.com
• Response with data
When master sends reading command, slave responds with the
corresponding set value or current status.
• Acknowledgement
When master sends setting command, slave responds by sending
the acknowledgement.
• Negative acknowledgement
When master sends a non-existent command or value out of the setting
range, the slave returns negative acknowledgement.
• No response
Slave will not respond to master in the following cases.
• Global address "FF" (MEWTOCOL) is set.
• Broadcast address "00H" (Modbus protocol) is set.
• Communication error (framing error, parity error)
• CRC-16 discrepancy (Modbus RTU mode)
• CS discrepancy (DL/T645)
1