EV/DV300 Series Power Meter
V:2.0 Revised October 2018
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2.3 Function code
The function code field of a message frame contains eight bits. Valid codes are in the
range of 1-255 decimal. When a message is sent from a master to a slave device the
function code tells the slave what kind of action to perform.
Table 4.2 Function code
Code
Meaning
Action
01
Read RO Status
us Obtain current status of Relay Output (ON/OFF)
02
Read DI Status
Obtain current status of Digital Input (ON/OFF)
03
Read data
Obtain current binary value in one or more registers
05
Control RO
Force Relay to a state of on or off (ON/OFF)
16
Preset Registers
Place bin value into consecutive Mutiple-Register
2.4 Data Field
The data field of message send from a master to slave device or from slave to master
contain additional information which the slave must use to take the action defined by
the function code or the result of action.
2.5 Error Check field
This field permits to check error during the data transmit process. A group of data
transmit from one device to the other may get error as there exist noise in transmission
line. The receiving device will not respond to the error message. The error check field
is based on a Cyclical Redundancy Check (CRC16) method.
3. Error Check
Error checking field is based on a Cyclical Redundancy Check (CRC) method. The CRC field
checks the contents of the entire message. It is applied regardless of any parity check method
used for the individual characters of the message. The CRC field is two bytes, containing a 16-
bit binary value. The CRC value is calculated by the transmitting device, which appends the
CRC to the message.
