Standardisation - RFID: Fundamentals and Applications in Contactless Smart Cards and Identification - page 248

PCB [CID] [NAD] [INF/APDU] CRC

< FSD/FSC

Figure 9.28 Structure of the frame in ISO 14443. The data of the application layer, Layer 7
(grey), are packed into the protocol frame of the transport layer (white)

b7 b6 b5 b4 b3 b2 b1 b0

00 0 chn cid nad 1 bnr

Block number
1 = NAD following

1 = CID following

1 Chaining

I-Block

=

b7 b6 b5 b4 b3 b2 b1 b0

10 0 ack cid 0 1 bnr

Block number
1

CID following
1 = NAK, 0 = ACK
R-Block

=

b7 b6 b5 b4 b3 b2 b1 b0

11 wtx cid 0 1 0

1 CID following

00b

=

= Deselect, 11b = WTX

S-Block

Figure 9.29 Coding of the PCB byte in a frame. The entire transmission behaviour is controlled
by the PCB (protocol control byte) in the protocol

The blocks are differentiated by different coding of the PCB (protocol control byte),
as shown in Figure 9.29.
The optional CID (card identifier) is used for addressing an individual smart card in
the interrogation zone of the reader. Thus, several smart cards can be activated at the
same time and addressed selectively using their CID. The NAD byte (node address)
was introduced in order to ensure compatibility between ISO 14443-5 and ISO 7816-3
(T 1). The use of this byte is therefore not further defined in ISO 14443.

In the case of an I block, the information field (INF) serves as a container for the
data of the application layer (APDU). The content is transmitted entirely transparently.
This means that the content of the protocol is forwarded directly without analysis
or evaluation.
Finally, a 16-bit CRC is appended as an EDC (error detection code) for error control.

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