Standardisation - RFID: Fundamentals and Applications in Contactless Smart Cards and Identification - page 246

FSDI (frame size device integer) defines the maximum number of bytes that
may be sent from the card to the reader in one block. Possible values for this are
16 , 24 , 32 ,... 128 and 256 bytes.
Furthermore, the smart card is allocated a CID (card identifier). Using the CID, it is
possible for a reader to maintain several Type A cards in a selected state at the same
time and to address an individual card selectively via its CID.
The ATS (answer to select) sent by the card in response to the RATS command
corresponds with the function of the ATR (answer to reset) of a contact smart card
and describes important protocol parameters of the smart card's operating system, so
that the data transmission between card and reader can be optimised in relation to the
properties of the implemented application.
Individually, the (optional) parameters listed in Table 9.12 can be contained in
the ATS.
Immediately after receiving the ATS, the reader can still initiate the changeover of
the transmission baud rates by sending out a special PPS command (protocol param-
eter selection). Based upon an initial baud rate of 106 Kbit/s, the baud rates in both
transmission directions can be increased independently of one another by a factor of 2,
4 or 8 if the smart card has signalled the support of higher baud rates in the optional
parameters DS and DR in the ATS.
Protocol The protocol described in ISO 14443-4 supports the transmission of appli-
cation data (APDU = application data unit) between the reader and the smart card.
The transmitted APDU can contain any desired data, such as command and response.
The structure of this protocol is based heavily upon the protocol T = 1 (ISO 7816-3)
that we know from contact smart cards, in order to keep the integration of this protocol

Table 9.12 The ATS describes important protocol parameters of the Type A card

Parameters Comment

FSCI frame size card integer: Maximum number of bytes that may be sent in a

block from the reader to the card

DS data rate send: Supported data rates of the smart card during the data

transfer from the card to the reader (possible values: 106, 204, 408,
816Kbit/s)

DR data rate send: Supported data rates of the smart card during the data

transmission from the reader to the card (possible values: 106, 204, 408,
816Kbit/s)

FWI frame waiting integer: This parameter defines the 'frame waiting time', i.e.

the maximum time that a reader has to wait after transmitting a
command for the response of the smart card. If no answer has been
received from the card after the end of this time, then a 'timeout' error
occurs in the communication

SFGI startup frame guard integer: This parameter defines the 'startup frame

waiting time', a special 'frame waiting time', that is valid exclusively for
the performance of the first application command after the ATS

CID supported
NAD supported

These parameters indicate whether the parameters CID (card identifier) and
NAD (node address) are supported by the smart card's operating system

Historical bytes The historical bytes contain additional, freely definable information on the

operating system of the smart card, e.g. a version number