Is there any timing specs between APDU/Response pair in smart card?

Question

Command response pair

I couldn't find a clear specification about the period between two consecutive Command/Response Pair (T in the diagram).

for example, If I had sent a command to the card and received a response, What is the maximum period I can wait before the communication is not valid anymore? I need this because I'm willing to make use of this period to give me some flexibility in my design.

Answer 1

This is the block waiting time (which can be computed from the BWI part of TB3 in the ATR). If the card needs more time, it has to send a Waiting Time Extension (abbreviated WTX), before this elapses, which has to be acknowledged by the other side (typically the reader). If the acknowledge is not given both sides assume a communication error.

Note, that FWI and BWI from TA1 as well as the clock supplied to the card influence the time.

Answer 2

For T=0, This would be the Waiting Time(WT). The ISO7816-3 spec gives the formula as:

WT = WI x 960 x (Fi/f)

Where
   WI = Waiting time factor. Normally this value is 10
   Fi = This value is obtained from TA1 in the ATR. Initially the value is 372
   f  = The clock speed