Sel 551 - Remote Bits; Reading Event Data Using Modbus

G.12
SEL-551 Relay Instruction Manual Date Code 20110408
Modbus RTU Communications Protocol
Modbus RTU Communications Protocol
Remote Bits
Command Code 0Ch-Control Remote Bits:
This code controls the remote bits. This command code has two parameters.
Parameter 1 determines the bit operation.
Parameter 2 determines which bit to control. It is bitmasked for future
expansion, but only one bit can be controlled at a time. The highest numbered
bit will be controlled if more than one bit occurs in the parameter.
Error Codes:
➤ If the relay is disabled while the commands are issued, the relay
will return error code 04 (device error).
➤ If the TRIGGER command cannot be executed due to multiple
events in progress, the relay will return error code 06h (device
busy).
➤ If the breaker jumper is not installed when a pulse output
command is issued, the relay will return error code 04h (device
error).
Reading Event Data
Using Modbus
The Modbus Register Map (Table G.18) provides a feature that allows you to
download complete event data via Modbus. The SEL-551 stores the 20 latest
15-cycle, full-length event reports. Please refer to Section 7: Standard Event
Reports and SER for more detailed description.
The event report will contain both analog and digital data. To download the
event data using Modbus, proceed as follows:
Step 1. Write the event number you wish to download at address
00B1h.
Step 2. Write the channel number you wish to download at address
00B2h.
Step 3. Read the four-sample per cycle event data from the Modbus
Map.
Value Operation
1Set
2Clear
3 Pulse (1/8 cycle)
Bit Pattern Remote Bit
0000 0000 0000 0001 RB1
0000 0000 0000 0010 RB2
0000 0000 0000 0100 RB3
0000 0000 0000 1000 RB4
0000 0000 0001 0000 RB5
0000 0000 0010 0010 RB6
0000 0000 0100 0000 RB7
0000 0000 1000 0000 RB8