FREE BROWSER TOOL
Modbus RTU frame builder
Build a standard read or write request and calculate its CRC16/Modbus trailer. The generated bytes are ready to compare with a serial capture.
- Unit ID
- 1
- Function
- FC03
- PDU address
- 0
- CRC order
- Low byte · high byte
REFERENCE
What the builder generates
The frame contains Unit ID, function-specific PDU fields, and CRC16/Modbus. Read quantities follow standard request limits. FC05 uses 0xFF00 for ON and 0x0000 for OFF.
A syntactically correct frame is not automatically safe to transmit. Verify the target, write permissions, process state, and recovery procedure before sending write requests to real equipment.