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2.12.2 Communication functions
Reading and writing of IC card data is performed by way of contactless communication between
an NFC module and an IC card. IC cards are preprogrammed to perform certain operations in
response to prescribed commands. When a command is correctly transmitted to an IC card, the
card responds to the received command by performing a corresponding operation. Once the
operation is complete, the card then transmits response information indicating the result of the
operation.
An explanation of the functions relating to this communication process is provided below.
Card polling function
1. Search for IC cards within the communicable range
2. IC card detection
3. IC card activation
4. Acquisition of IC card response information
The card polling function terminates the search for IC cards when: it detects a smart card; the
timeout elapses; the assigned callback function returns a 'FALSE' value; or the 'stop polling'
function is executed.
Once the IC card has been successfully activated, the NFC module continually transmits radio
waves in order to supply power to the smart card. This radio wave transmission terminates
automatically when the 'radio off' function is executed or when a certain time elapses without any
data communication between the NFC module and the IC card. It is possible to enable or disable
the automatic stop (auto stop) setting and to change the time until the auto stop occurs (i.e. the
timeout). Under the default settings, auto stop is enabled and the timeout is set at 1,000
milliseconds.
* If there are multiple IC cards within the communicable range, it is not possible to start just one
of them, or all of them. It is necessary to bring each IC card into proximity one card at a time in
order to ensure proper communication.
Data communication functions
Data communication becomes possible once the IC card has been activated by the card polling
function.
Communication ends once the NFC module has received response information from the IC card in
response to a transmitted command, or when the timeout elapses.
When the communication is successful, the IC card remains in the activated mode, thus enabling
consecutive transmission of other data.
Function Description Termination criteria Timeout
Card polling
Function
Searches for IC cards
within communicable
range and, upon
detection, activates
the card and obtains
its response
information
The card is successfully
activated and card information
is obtained
Timeout elapses
Assigned callback function
returns 'FALSE'
'Stop polling' function is
executed
100-60,000msec
or
no timeout
Data
communication
Data communication
can be performed with
IC card response reception is
complete
60msec
*1
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