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13. ANNEX 3. MODBUS
This annex describes the fundamentals about the communication with MIF units using ModBus
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
01
03
Reply:
ADDRESS
FUNCTION
01
03
GEK-106273L
ANNEX 3 MODBUS MEMORY MAP
®
MEMORY MAP
BEGINNING
#REGS
04FE
004B
BYTES
DATA0
...
96
500D
MIF Digital Feeder Protection
CRC
653D
DATA74
CRC
0200
84 D5
®
protocol. The
13-1
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