如何在iso14443a初始化和防冲突中对RATS命令进行编程

Question

please i will like to know how to change some bytes in the Request for answer select command (RATS) that the reader sends to a card during initialization phase. At the moment my NFC reader acr122u send an FSD byte of 5 in the RATS command, and after some research i found out that FSD with a value of 5 means that the terminal only accepts frame sizes with a max size of 64bits and i need to send more than that in one apdu. Could someone please help

Answer 1

The ACR122U is built with the NXP PN532 NFC controller so you're limited to what functions it supports. From looking through the PN532 User Manual, it doesn't seem to offer configuration of the RATS explicitly. The SetParameter command only lets you enable/disable Automatic RATS generation but not tweak it's bits. I also found that the Manual doesn't refer to FSD as the NFC Forum spec does, but as FSL:

The FSL parameter of PSL_REQ is fixed to 0x00, meaning that the maximum length of the Transport protocol field is 64bytes.

You might try using a newer product like the ACR1252 or ACR35 that will likely have a newer, more customizable NFC controller.

Answer 2

(Assuming you are developing your own PICC):

You have to implement the chaining feature as described in the ISO/IEC 14443-4 (chapter 7.5.2).

(If I recall correctly, you need to transmit your response data in multiple I-blocks and set the chaining bit for all, but the last block. These I-blocks are handled in the same way as any other I-block , ie acknowledge. re-transmitting, etc. takes place).

There is an example in the ISO/IEC 14443-4.