Newbie level 1
How to connect Siemens PLC S7-200 on Serial Port without any third party Drivers or APIs?
Please tell me About Modbus Protocol or Profibus Protocol for S7-200.
Member level 1
You can use Open Serial Protocol features of S7-200 PLC. I don't remember now exactly, but it works with XMRT and RXT mnemonics of Statement List language.
Go through its System Manual and you will find examples there.
Member level 2
how to read data siemens from plc using .net
If you want to transmit/receive data to or from another equipment you should have a cable (PPI cable, RS232-RS485 cable).
In PLC lader, you init SMB30 cell with rev./trans configure, for example: value 16#09 in SMB30: baud rate: 9600bps, 8 bit data, 1 stop bit, no parity
after that, you using XMT for transmit (using help on program) or interrupt 8 to receive data
It is easy for you to do this, good luck!
Full Member level 3
Check at S7-200 documentation for freeport configuration. Take a look at special memory bytes SMB30 for Port 0 and SMB130 for Port 1. After port configuration you can use the XMT and RCV function to send and receive a number of data bytes. Check these functions how they work, in help.