ROOTCASTLE / ENGINEERING LAB
Protocol inspector
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 }
Airson a bheil iad airson
Is e na faileasanna coitcheart a tha ann an co-dhùnadh a’ chlàraich: CRC deaslach, seòrsa deaslach, bun-òrdugh a chur air falbh agus àm-ghairean. Gluaisibh frèam a chòip a thug sibh bho aghaidh no log sìor-ghnìomhach chun a chur air aghaithe a tha deaslach, an cod deaslach aig an àm-ghaire agus na chur-sìos a tha air a chur air aghaidh air luachan clàraich.
Lìonachaisean
Cha bhi an toll a’ cumail còmhlaich ri àm-ghairean no a’ cur data a-mach; gach comas a’ rùnadh ann do bhrabhsair. Modbus ASCII, Modbus TCP, CAN FD agus J1939/CANopen a’ cur-sìos air pàipearan a tha gun sgeul. Is urrainn an stiùireadh a bhith deaslach airson frèaman neònach; roghnaichibh e beò.
References
Modbus over Serial Line V1.02 · Modbus Application Protocol V1.1b3 · ISO 11898-1:2015 (CAN data link layer) · CRC catalogue
Mòdell foghlam. Chan eil na comharrachadh gu h-òmhair airson diùcadh a-mach ri machan-aillean no a thogail leasachaidhean sòisealta.