1MDU07205-YN rev. F
REF601 CEI
User’s manual
79
7.4.2 Function Code: 04 (Read Data log, Event log, Measurement of
Phase and Earth current)
This function code is used to read data log of last two events and event log of last
fi ve events occurred in the relay. The same function code is also used to read the
phase and earth current (i.e. I1-I2-I3-I0). The mapping of current measurement is 1In
= 1000. For example, a current value of 2In will be displayed in Hex format as 0x07D0
(2000 in decimal). The measurement will not be a real time measurement but it will be
a query based communication between the base relay and the communication board
and subsequently for the modbus.
The request packet specifi es the starting register address and the number of registers.
The register data in the response message are packed as two bytes per register, with
the binary contents right justifi ed within each byte. For each register, the fi rst byte
contains the high order bits and the second contains the low order bits.
Slave
Address
Function
Code
Starting
Address
High
Starting
Address
Low
Quantity
of
registers
High
Quantity
of
registers
Low
CRC CRC
01 04 00 01 00 16 CRC CRC
Request
Example: Read data_0 log from slave at address 01.
Slave
Address
Function
Code
Byte
Count
Data1
Hi
Data1
Lo
Data
16 Hi
Data
16 Lo
CRC CRC
01 04 20 05 01 C0 F6 CRC CRC
Response message format for function code 04
In the response the data log of the last event is shown as data bytes. The byte count
provides the number of bytes that will follow.
The register mapping of data log is shown in table - 6, event log is explained in table
– 7, 8, 9, and register mapping for current measurement is shown in Table 10.
Serial Communication
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