JavaCard OS

Hi friends in here,

I have a question about Le in APDU command.

If I don't know how many data I will have in response, is there any special value of Le for this case?

Thanks.

If you don't know how many bytes to expect, just set Le to 0x00. It will help you get all the data back.

But there is a special case.

If your card supports T=0 protocol, you will get error state 0x 6C NN (NN is the actually the bytes length the card will give you).
At this time, you should re-send the APDU command with correct Le NN to get the data.