A-2 MIB High Impedance Bus Differntial Relay GEK-106426B
A.1 READING VALUES APPENDIX A
A
A.1READING VALUES
The ModBus
®
function used is number 3 (READ HOLDING REGISTERS). The information retrieved from the relay is in
Intel format (little endian), that is to say, ordered from lower to higher weight (first the least significant byte, then the next
least significant byte and so on until the most significant one, that will go last). The message request command is
generated as follows:
Request:
Reply:
Example:
Reading 75 registers (150 bytes) beginning from address 04FEH (1278) .
Request:
Reply
FIELD LENGTH
Relay address 1 Byte
Function 1 Byte (03h)
Beginning address 1 word (High Byte – Low Byte)
Number of registers 1 word (High Byte – Low Byte)
CRC 1 word
FIELD LENGTH
Relay address 1 Byte
Function 1 Byte (03h)
No. of bytes 1 Byte
Value of the registers n data bytes /2 words (from lowest byte to
highest byte)
CRC 1 word
ADDRESS FUNCTION BEGINNING #REGS CRC
01H 03H 04FEH 004BH 653DH
ADDRESS FUNCTION BYTES DATA0 ... DATA74 CRC
01H 03H 96H 500DH 0200H 84D5H
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