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CCID Packet (256 bytes)
1
st
64 byte chunk
2
nd
64 byte chunk
3
rd
64 byte chunk
4
th
64 byte chunk
At least 2 character
idle time (~200
µ
s)
At least 3 ms idle
time for EOP
Figure 10. Example data transfer of a 256-byte data packet
The entire CCID packet including the header is broken down into 64-byte packets, which are
transmitted one at a time. Ensure that there is at least a two-character idle time (approximately 200
microseconds) between consecutive 64-byte chunks. This idle time gives an opportunity for the
serial device to save and clear its receiving buffer. The last data packet can be less than 64 bytes
long. End-of-packet (EOP) is indicated by at least three milliseconds of idle time.
When EOP
is received by the module, it internally checks the CCID packet’s length indicated in the
CCID packet header.
•
I
f the CCID packet header’s length is equal to (or less than) the received CCID packet length,
then the module processes that packet.
•
If
the CCID packet header’s length is more than the received CCID packet size length, then the
module waits for the next 64-byte chunk to arrive.
Note: When a CCID packet transmission starts, the first 64-byte chunk includes the CCID header,
which indicates the slot ID where the data is being sent to or received from.
Each command message sent to a particular reader receives an appropriate response from the
NFC module. The serial host does not send another command message to a reader until it receives
a response. However, the serial host may send command messages concurrently to different
readers at the same time. The NFC module may not respond in the same sequence as the sent
commands. The response depends on the internal priority of the readers and the time taken to
process the request by the media.
6.3 Notifications and data exchanges (serial connection)
6.3.1 Media arrival and removal notification
The NFC reader sends out three bytes to notify media arrival or removal. The format of these three
bytes is shown in Table 13.
Table 13. Media arrival or removal
1
st
Byte
2
nd
Byte
3
rd
Byte
Always
[0x50]
Slot / media status
Media type
Slot / media status
The first most significant 4 bits denote the reader slot ID. The least 4 bits denote the media status. If
media status is 0 then the media is not present. If it is 1, then the media is present.