Smart card PC emulator

[timaco]

How do you keep the data transmitted from TXD(pin8) from going back to RXD(pin7)?

[MP]

You should post a link to the project in your post so that we do not need to leave the forum to go look. Otherwise, we will have to log back on and find your post again.

MP

[hotwaterwizard]

Looks Like this is his first Post on our board Here is the Link to the project he is refering to:

Smart Card PC Emulator JUST CLICK HERE

[MP]

Thanks John, I was lost.

Timaco welcome to the community:
This circuit is dependent upon the device not sending and receiving at the same time. This is how half-duplex transmission works. I have seen quite a few manufacturers do this to save a few parts when full duplex is not needed for the circuit to operate.
Here is a link to a site that gives a very good explanation of the two communication methods with an illustration for a cable:
http://www.viddata.com/cables.htm

Hope this helps.

MP