How to communicate between S7-300 and PC?

[Qia.sky]

I have a PC with serial port, and S7-300 with a module CP340.
So Can I communicate(Read/Write) between them? Do I need make a protocol?

As far as I know S7-300 has two Function blocks(FB3&FB4) which they can receive or send.but I don't know the detail of communication.
Somebody could give me some hint.Thx a lot.

[JenK]

What environment are you trying to use? Here are a couple of related discussion forums:

http://forums.ni.com/ni/board/message?board.id=170&message.id=85365&requireLogin=False

http://digital.ni.com/public.nsf/websearch/4EC8A6E115FDD1AA862566C50067F954?OpenDocument

http://forums.ni.com/ni/board/message?board.id=260&message.id=17&requireLogin=False

http://forums.ni.com/ni/board/message?board.id=190&message.id=680&requireLogin=False

Please repost if you have further questions.

JenK

[Qia.sky]

Thank you reply,JenK

The documents above seem like I need more adaptor or device to communicate with S7-300 PLC.
But my boss need to cut the price of initial cost, so there is a low cost way to do ?

So far I can read the data from serial port which connect with CP340 module's RS232 port.
but I don't know how to modify the PLC's register value so that I can control the the whole process.
Are there cheaper way except profibus using lookout?

BTW, I use this communication in HVAC system.

[JenK]

Here are some tutorials about how to do serial communication in Lookout. They could be what you are looking for.

http://zone.ni.com/devzone/conceptd.nsf/webmain/8c5206e2c4c9dfc186256ddd0056e46f?OpenDocument
http://zone.ni.com/devzone/conceptd.nsf/webmain/033CD84BAC7E1E7586256A3300756284?opendocument
http://zone.ni.com/devzone/conceptd.nsf/webmain/afcb969df200646886256db9005bdb87?OpenDocument

Hope this is more of a help.

JenK