GE TRANSFORMER MANAGEMENT RELAY 745 Instruction Manual page 180

7.3 MODBUS FUNCTIONS
For an example of how to use the User Map feature, say the master computer is required to continuously read the memory
map locations shown below from slave 11. Normally, this would require at least 4 separate master query messages.
ADDRESS DESCRIPTION
0200H Relay Status
0210H W3 Phase Time O/C Flag
0300H W1 Phase A 4th Harmonic Content
0301H W1 Phase B 4th Harmonic Content
0302 hex W1 Phase C 4th Harmonic Content
2002 hex Percent Differential Pickup
1. First, preload the addresses listed in the first column of the table to in User Map Addresses #1 to #6 (addresses 0180
to 0185 hex).
MASTER QUERY MESSAGE:
SLAVE ADDRESS
FUNCTION CODE
DATA STARTING ADDRESS: high order byte, low order byte
NUMBER OF SETPOINTS: high order byte, low order byte
BYTE COUNT
DATA #1: high order byte, low order byte
DATA #2: high order byte, low order byte
DATA #3: high order byte, low order byte
DATA #4: high order byte, low order byte
DATA #5: high order byte, low order byte
DATA #6: high order byte, low order byte
CRC: low order byte, high order byte
SLAVE RESPONSE:
SLAVE ADDRESS
FUNCTION CODE
DATA STARTING ADDRESS: high order byte, low order byte
NUMBER OF SETPOINTS: high order byte, low order byte
CRC: low order byte, high order byte
2. Now that the User Map Addresses have been setup, the required memory map locations can be accessed via the User
7
Map Values #1 to #6 (addresses 0100 to 0105 hex). Both actual values and setpoints may be read.
MASTER QUERY MESSAGE:
SLAVE ADDRESS
FUNCTION CODE
DATA STARTING ADDRESS: high order byte, low order byte
NUMBER OF REGISTERS: high order byte, low order byte
CRC: low order byte, high order byte
SLAVE RESPONSE:
SLAVE ADDRESS
FUNCTION CODE
BYTE COUNT
DATA #1: high order byte, low order byte
DATA #2: high order byte, low order byte
DATA #3: high order byte, low order byte
DATA #4: high order byte, low order byte
DATA #5: high order byte, low order byte
DATA #6: high order byte, low order byte
CRC: low order byte, high order byte
7-10
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TYPE
actual value
actual value
actual value
actual value
actual value
setpoint
EXAMPLE (HEX):
11 query message for slave 11
10 store multiple setpoint values
01 80 data starting at address 0180
00 06 6 setpoint values = 12 bytes total
0C 12 bytes of data
0200 → Relay Status
02 00
0210 → W3 Phase Time O/C Flag
02 10
0300 → W1 Phase A 4th Harmonic Content
03 00
0301 → W1 Phase B 4th Harmonic Content
03 01
0302 → W1 Phase C 4th Harmonic Content
03 02
2002 → Percent Differential Pickup
20 02
2F 8A CRC computed by master
EXAMPLE (HEX):
11 response message from slave 11
10 store multiple setpoint values
11 80 data starting at address 0180
00 06 6 setpoint values = 12 bytes total
42 8F CRC computed by slave
EXAMPLE (HEX):
11 query message for slave 11
03 read register values
01 00 data starting at address 0100
00 06 6 setpoint values = 12 bytes total
C6 A4 CRC computed by master
EXAMPLE (HEX):
11 response message from slave 11
03 read register values
0C 6 registers values = 12 bytes of data
82 01 Relay Status
00 01 W3 Phase Time O/C Flag = not operated
W1 Phase A 4th Harmonic Content = 1% ƒ
00 01
W1 Phase B 4th Harmonic Content = 1% ƒ
00 01
W1 Phase C 4th Harmonic Content = 1% ƒ
00 01
Percent Differential Pickup = 0.30 × I
00 1E
80 F1 CRC computed by slave
745 Transformer Management Relay
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