| ??? 12/02/09 07:18 Read: times |
#171377 - Modbus Responding to: ???'s previous message |
I have a another PLC with standard Modbus running and it captures the requires value from the desired PLC and displays it on its own screen. So, it is sure that the desired PLC is working.
The Modbus program don't receive any answer, no error message or anything. How do you know that 9600 baud is the correct speed? -The desired PLC is communication with another PLC at modbus (RS232) How do you know that there shouldn't be any parity? -Should there be any...? How do you know that your null-modem cabling is correct? -The same is working with another PLC... How do you know that your null-modem cabling is correctly connected? -The same is working with another PLC... How do you know that the device is using RTU? -The other PLC is working in both modes with the desired PLC... How do you know that the device have Modbus enabled? -The same is working with another PLC... How do you know that the request is reaching the device? -If the Hyper Terminal is receiving the message then the PLC should How do you know that the device isn't answering, but the answer not reaching the PC? -This is not possible,I am handling the Rx, Tx with separate MCUs How do you know that your timing is ok? -In the same scenario of the other PLC... |
| Topic | Author | Date |
| Modbus | 01/01/70 00:00 | |
| What testing have you done? | 01/01/70 00:00 | |
| Don't use hyperterminal | 01/01/70 00:00 | |
| modbus | 01/01/70 00:00 | |
| modbus | 01/01/70 00:00 | |
| Still lots of debugging left | 01/01/70 00:00 | |
| Modbus | 01/01/70 00:00 | |
| Not very helpful | 01/01/70 00:00 | |
| Modbus | 01/01/70 00:00 | |
| Still need to break the problem down into smaller steps | 01/01/70 00:00 | |
| Modbus | 01/01/70 00:00 | |
| modbus | 01/01/70 00:00 | |
| modbus | 01/01/70 00:00 | |
| Parity | 01/01/70 00:00 | |
| Oscilloscope results? | 01/01/70 00:00 | |
| open source | 01/01/70 00:00 | |
| Also RTU Framing | 01/01/70 00:00 | |
| Framing, addressing etc has been discussed | 01/01/70 00:00 | |
| modbus | 01/01/70 00:00 | |
| Bad CRC order!! | 01/01/70 00:00 | |
| modbus | 01/01/70 00:00 | |
| modbus | 01/01/70 00:00 | |
| Don't know why, | 01/01/70 00:00 | |
| Comparison with something known working | 01/01/70 00:00 | |
| what device address | 01/01/70 00:00 | |
| modbus | 01/01/70 00:00 | |
I would do this... | 01/01/70 00:00 |