# Issue in RS232 Communication by COM1 port in Delta DVP28SV11T2 PLC **URL:** \ **Category:** Ignition\ **Created:** [November 25, 2024, 5:29pm UTC](https://forum.inductiveautomation.com/t/issue-in-rs232-communication-by-com1-port-in-delta-dvp28sv11t2-plc/99082 "2024-11-25T17:29:58Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![DAKSHAK\_DABHADE](https://avatars.discourse-cdn.com/v4/letter/d/848f3c/32.png) [@DAKSHAK\_DABHADE](https://forum.inductiveautomation.com/u/DAKSHAK_DABHADE)\ **Post date:** [November 25, 2024, 5:29pm UTC](https://forum.inductiveautomation.com/t/issue-in-rs232-communication-by-com1-port-in-delta-dvp28sv11t2-plc/99082/1 "2024-11-25T17:29:58Z")
Dear Team its urgent. I have DVP28SV11T2 PLC having problem with Communication by RS232 which is done by COM1 Port, I have all correct PLC program for communication H91 is moved in D1036 register used for COM1 (RS232) port. and retained communication protocol by setting ON M1138 and selecting RTU mode by setting Bit ON M1139. its was working since 6 years but now sudden im facing communication problem. also, the parameters set in connected device are correct as set in PLC D1036 above (H91 means 19200 baudrate, stopbit:1,parity: None, data length:8). Using standard Communication cable DVPACAB2A30. also tried to read data in Modscan no response. please suggest is the problem in port or other? ---
**Author:** ![pturmel](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/pturmel/32/3295_2.png) [@pturmel](https://forum.inductiveautomation.com/u/pturmel)\ **Post date:** [November 25, 2024, 5:32pm UTC](https://forum.inductiveautomation.com/t/issue-in-rs232-communication-by-com1-port-in-delta-dvp28sv11t2-plc/99082/2 "2024-11-25T17:32:52Z")
> [@DAKSHAK\_DABHADE](#): > > also tried to read data in Modscan no response. Sounds like a hardware failure in your PLC. ---
**Author:** ![DAKSHAK\_DABHADE](https://avatars.discourse-cdn.com/v4/letter/d/848f3c/32.png) [@DAKSHAK\_DABHADE](https://forum.inductiveautomation.com/u/DAKSHAK_DABHADE)\ **Post date:** [November 25, 2024, 5:38pm UTC](https://forum.inductiveautomation.com/t/issue-in-rs232-communication-by-com1-port-in-delta-dvp28sv11t2-plc/99082/3 "2024-11-25T17:38:04Z")
Dear sir, Ok Thanks for the Immediate response. ---
**Author:** ![pturmel](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/pturmel/32/3295_2.png) [@pturmel](https://forum.inductiveautomation.com/u/pturmel)\ **Post date:** [November 25, 2024, 5:39pm UTC](https://forum.inductiveautomation.com/t/issue-in-rs232-communication-by-com1-port-in-delta-dvp28sv11t2-plc/99082/4 "2024-11-25T17:39:21Z")
If you were running Modscan from the same computer as Ignition, it could mean the PC's serial port failed. If so, try Modscan from a separate PC. I should mention that N-8-1 is not valid, per the Modbus RTU specification. That specification requires two stop bits if no parity is used. Are you sure N-8-1 is correct for your system? ---
**Author:** ![DAKSHAK\_DABHADE](https://avatars.discourse-cdn.com/v4/letter/d/848f3c/32.png) [@DAKSHAK\_DABHADE](https://forum.inductiveautomation.com/u/DAKSHAK_DABHADE)\ **Post date:** [November 27, 2024, 7:47am UTC](https://forum.inductiveautomation.com/t/issue-in-rs232-communication-by-com1-port-in-delta-dvp28sv11t2-plc/99082/5 "2024-11-27T07:47:10Z")
Yes sir, Thanks for reply.. I am running Modscan from separate computer + i also verified N-8-1 is all correct in both side. & also it was working before on the same parameters. ---
**Author:** ![pturmel](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/pturmel/32/3295_2.png) [@pturmel](https://forum.inductiveautomation.com/u/pturmel)\ **Post date:** [November 27, 2024, 12:13pm UTC](https://forum.inductiveautomation.com/t/issue-in-rs232-communication-by-com1-port-in-delta-dvp28sv11t2-plc/99082/6 "2024-11-27T12:13:12Z")
Then my original diagnosis is probably correct. The COM port in the PLC has failed.