GE GEK-106273L, Instruction Manual

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ANNEX 3 MODBUS MEMORY MAP
GEK-106273L MIF Digital Feeder Protection 13-1
13. ANNEX 3. MODBUS
®
MEMORY MAP
This annex describes the fundamentals about the communication with MIF units using ModBus
®
protocol. The
references to memory addresses can vary depending on the model, or between different firmware versions; for this
reason, you must make sure that you have the appropriate memory map for your MIF model and firmware version.
To make this easy, the ENERVISTA MII SETUP software supplied with M Family units incorporates, in versions 1.8
and higher, a tool that allows to extract the memory map of any M Family unit (MIF, MIV, MIG, MIN, MIW, etc.)
connected to the PC.
13.1 READING VALUES
The MODBUS
®
function used in this case is number 3 (READ HOLDING REGISTERS). The message request
command is generated as follows:
Request:
FIELD LENGTH
Relay address 1 Byte
Function 1 Byte (03H)
Beginning address 1 word (High Byte– Low Byte)
Nº records 1 word (High Byte– Low Byte)
CRC 1 word
Reply:
FIELD LENGTH
Relay address 1 Byte
Function 1 Byte
No. of bytes 1 Byte
Value of the records No. of bytes/2 words
CRC 1 word
Example:
Request:
Reading of 75 records (150 bytes) beginning from address 04FE (1278).
ADDRESS FUNCTION BEGINNING #REGS CRC
01 03 04FE 004B 653D
Reply:
ADDRESS FUNCTION BYTES DATA0 ... DATA74 CRC
01 03 96 500D 0200 84 D5