Unable to parse serial port output between ISO 7816 and Reader

Question

I'm trying to interpret the communication between an ISO 7816 type card and the card reader. I've connected inline between the card and the reader when i dump the ouput to console i'm getting data that that im not expecting, see below:

Action: Card inserted to reader, expect an ATR only

Expected output:

3B 65 00 00 B0 40 40 22 00

Actual Output:

E0 3B 65 00 B0 40 40 22 00 90 00 80 9B 80 E0 E2

The 90 00 is the standard for OK that it reset, but why i am still logging additional data both before the ATR (E0) as well as data after

Answer 1

The communication line is documented in ISO 7816-3 (electrical interface and transmission protocols), look for the respective chapters of T=0 or T=1 protocol. T=1 is a block oriented protocol involving a prolog containing node addresses and an epilog containing a CRC/LRC.

For the ATR however, no protocol is running yet, since here the information is contained, which protocols the card supports, for the terminal to choose. Surely so early 90 00 is no SW1/SW2.