GE 845 Instruction Manual page 139

CHAPTER 4: SETPOINTS
845 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
SLAVE RESPONSE
DIAG CODE
DATA
CRC
Function Code 10H
Modbus Implementation: Preset Multiple Registers
845 Implementation: Store Multiple Setpoints
The function code allows multiple Setpoints to be stored into the 845 memory. Modbus
"registers" are 16-bit (two byte) values transmitted high order byte first. Thus all
845 setpoints are sent as two bytes. The maximum number of Setpoints that can be stored
in one transmission is dependent on the slave device. Modbus allows up to a maximum of
60 holding registers to be stored. The 845 response to this function code is to echo the
slave address, function code, starting address, the number of Setpoints stored, and the
CRC.
For example, consider a request for slave 17 to store the value 00 02 to setpoint address
045C and the value 01 F4 to setpoint address 04 5D. After the transmission in this example
is complete, 845 slave 17 will have the following setpoints information stored:
Address
04 5C
04 5D
Table 4-18: Master Packet Format for Function Code 10H
MASTER TRANSMISSION
SLAVE ADDRESS
FUNCTION CODE
DATA STARTING ADDRESS
NUMBER OF SETPOINTS
BYTE COUNT
DATA 1
DATA 2
CRC
Table 4-19: Slave Packet Format for Function Code 10H
SLAVE RESPONSE
SLAVE ADDRESS
FUNCTION CODE
DATA STARTING ADDRESS
NUMBER OF SETPOINTS
CRC
Administrator Login and Commands via Modbus for 8 Series Relays
Logging in as Administrator
Logging in as Administrator is demonstrated in the example below. The process requires
writing 44 bytes which consist of the Role ID and Password. Password characters are 22
bytes and role characters are also 22 bytes. The logging in must be done using a single
Modbus command using Function 10H (Store Multiple Setpoints).
The following table shows data to be written to the relay to login as Administrator. The
relay password in this example is 0.
BYTES EXAMPLE
2 00 00
2 00 00
2 E0 0B
Data
00 02
01 F4
BYTES EXAMPLE
1 11
1 10
2 04 5C
2 00 02
1 04
2 00 02
2 01 F4
2 31 11
BYTES EXAMPLE
1 11
1 10
2 04 5C
2 00 02
2 82 7A
DESCRIPTION
must be 00 00
must be 00 00
CRC error code
DESCRIPTION
message for slave 17
store setpoints
setpoint address 04 5C
2 setpoints – 4 bytes total
4 bytes of data
data for setpoint address 04 5C
data for setpoint address 04 5D
CRC error code
DESCRIPTION
message from slave 17
store setpoints
setpoint address 04 5C
2 setpoints
CRC error code
DEVICE
4–35