Table of Contents
Advertisement
MODBUS - OPERATIONS
All registers are assigned to Holding Registers, which can be read out with Read Holding Registers or Read Input Registers
command. If reading an address with no assigned register is attempted, '0' is given.
Write Multiple Registers command is used to write in registers. If writing an address with no assigned register is attempted,
'Exception' is given.
FUNCTION
03
04
16
These commands enable reading measured values and writing configurations.
One (1) word registers are represented in 16-bit integers, while two (2) word registers are in 32-bit. All registers are in the
form of signed integer unless specifically given in the explanations.
The lower digit word in a 32-bit register is assigned to the lower address (n), while the upper digit word is assigned to the
higher address (n+1).
Address
n
Contents
Lower digit word
The 32-bit register (2 words) must be read out and written in single command sequence.
It is recommended to wait for a time period indicated under 'recommended time out value' in the above table to receive a
response for a command. If no response is received for these time periods, take appropriate error processing such as retrying.
■ MODBUS REGISTER ACCESS SETTING
ADDR.
WORD
PARAMETER
4943
2
Deactivate Modbus register writing protection
Writing a preset passcode in this register deactivates the writing protection via Modbus.
When the Modbus passcode set in this register matches the preset one, setting '1' or '2' in the register address
4945 becomes available to enable writing in Modbus registers.
Reading out the register value is not possible. It reads always '-1' regardless of the code setting.
After writing is complete, be sure to set a value other than the passcode ('0' is recommended) to activate the
writing protection again.
4945
1
Modbus register access setting
0 : Write disable (*)
1 : Write enable
2 : Write enable the count values
Other : Write disable
This setting is erased when the power supply to the unit is removed. It always starts with '0' (Write disable)
when the power supply is turned on. Set '1' or '2' before starting writing at other registers.
In order to write a count value (e.g. active energy), set '2' at this register address. When it is set, the unit stops
counting so that a new count value can be written in the register address. Be careful to use '2' setting because
no counting will be performed if the unit remains with this setting.
When the Modbus register writing protection is enabled, this register setting cannot be changed from '0' to '1' or
'2' unless a correct security code is set in the address 4943.
(*) Factory setting
COMMAND
Read Holding Registers
Read Input Registers
Write Multiple Registers
n + 1
Upper digit word
5-2-55, Minamitsumori, Nishinari-ku, Osaka 557-0063 JAPAN
Phone: +81(6)6659-8201 Fax: +81(6)6659-8510 E-mail: info@m-system.co.jp
EXPLANATION
Used to read registers
Used to read registers
Used to write in registers
R7EWTU
RECOMMENDED TIME OUT VALUE
0.5 seconds
0.5 seconds
2 seconds
EM-7818 Rev.2 P. 7 / 18
Advertisement
Table of Contents
