ROOTCASTLE / ENGINEERING LAB
Inspector ng protocollo
Decode Modbus RTU, UART and CAN frames.
LOCAL CALCULATION · NO DEVICE CONNECTION
Modbus RTU decoder
✓ Valid frame · Request
| Field | Bytes | Value |
|---|---|---|
| slave | 01 | 1 |
| function | 03 | 3 Read Holding Registers |
| start | 00 00 | 0 (0x0000) |
| quantity | 00 0A | 10 |
| crc | C5 CD | 0xCDC5 = 0xCDC5 |
Model and assumptions
RTU frame: address, function, data, CRC-16 (reflected polynomial 0xA001, initial 0xFFFF, low byte first). The same function code has different lengths in request and response; automatic direction can be wrong for ambiguous frames. Addresses are zero-based; the 40001 notation is a device convention. Word order of 32-bit values depends on the device.
CRC: c=0xFFFF; c^=byte; 8×{ c = c&1 ? (c>>1)^0xA001 : c>>1 }
Para saan ito gamit
Ang mga pinakamadalas na field communication faults ay mali na CRC, mali na address, na-mix ang word order, at timeouts. Paste ang isang frame na kopiado mula sa analyser o serial log upang makita kung anong field ang mali, ang device exception code at ang mga likely interpretations ng register values.
Mga limitasyon
Ang tool ay hindi nakakonekta sa devices o nagpo-post ng data; bawat calculation ay nagrerun sa iyong browser. Modbus ASCII, Modbus TCP, CAN FD at J1939/CANopen payload interpretation ay labas ng scope. Ang automatic direction ay maaaring mali para sa ambiguous frames; piliin nang manual.
References
Modbus over Serial Line V1.02 · Modbus Application Protocol V1.1b3 · ISO 11898-1:2015 (CAN data link layer) · CRC catalogue
Educational model. Ang results ay hindi sapat para magdiagnose ng machine o mag-establish ng safe operating limits.