Hello,

Tharun______66

I want my PLC to act as a slave that sends 10 modbus addresses for which I have used send ptp block?

is that correct or I have to use some other block?

 no. For first and also as I said before, you want use Modbus RTU protocol or other type of protocol? In case of Modbus RTU you need use Modbus blocks for data exchange. In case you ask for data from PC Modbus application then your PLC is Slave so you need cfg your PLC in this way, with MB_SLAVE or Modbus_Slave block. For proper cfg of communication settings you need use MB_COMM_LOAD or Modbus_Comm_Load blocks. You can't use standard SEND/RECV blocks because there isn't Modbus protocol implemented. I recommend for first check web page www.simplymodbus.ca to improve knowledge and then TIA portal help to my mentioned blocks used. On other side, your RS232 cable need have TX/RX pins swapped at one side of cable of course. It is enough to have 3 pins in cable - TX,RX and GND for functionality. I'll attach some example prj link here after while...

Example: How to configure Modbus RTU with S7-1200 CPU

This example cover RS485 module but it is good example also to your situation because of used blocks and configuration. I expect differencies especially with different CM module interface type signals - RS422/485 to your actual RS232.

Hello,

pls attach also ZIP screenshots from your PC app with set parameters to see if you set correct requests. It is simply not easy find problems if you send only one side cfg because important requests are set at Master PC app in this case. If you receive errors message from Slave, save also this screenshot from PC app. Just one important thing, I see your blocks are green outlined in Online mode what can indicate correct initialisation. Can you confirm (because I don't see your check STATUS, ERROR, DONE conditions in code) that you have some conditions to check some of that output parameters values for sure? It is maybe then easy check if Master sends some not correct requests or other ERROR/STATUS values?

Important thing!

I see from your screenshot that your PLC cfg is with errors (red indication on left side of prj tree). can you confirm what error you have? Also pls confirm, you set REQ for Comm_Load block initially to TRUE and check DONE or ERROR for TRUE? Simply it is expected to do logical steps although I see that green outlined blocks, I ask you to do this for sure.

Hello,

2 problems probably at your side:

1. your Slave block define Slave address 16 but your PC SW device ID of Slave is 1.

2. your PLC Holding register has only 11 elements but you ask with PC for number of 20 registers.

Hello,

user

I also checked the done/error in my comm_load block, but both are in false. I believe done should be true. what may be the cause. should I change the req in comm load block to clock pulse so that it can req more often?

you need check that with your code, no visually. After it is DONE->TRUE or ERROR true then you can set REQ to FALSE, it need to be reinit only after start of PLC or if some ERROR due cfg is set and you need init cfg of Port again. Pls take a look at your last screenshot about CM cfg, Comm_Load do this cfg.