This smartcard adapter follow exactly the specification ISO 7816. Also, the protocol is the `asynchronous half duplex T=0 protocol` with `active low reset` and `inverse convention` as defined in this standard.
The following description may be used in order to connect computers to ISO 7816 compatible chip card systems (e.g. GSM mobile phones or other pay-TV decoding systems) if they also use asynchronous transmission. For smart card systems which use synchronous transmission (e.g. most phone cards) the interface described here will need some modifications.
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According to ISO, a chip card is 85.60 mm long, 53.98 mm high, 0.76 mm thick and the edges are rounded with a radius of 3.18 mm. It has eight defined contact areas (C1 - C8 in the diagram below), each of which is at least 2 mm wide and 1.7 mm heigh.
The pins DTR, DSR and CTS are not actually needed, they are just connected together in the adapter, so that defined levels are available on them because some software might need this.
The MAX232 converts the RS-232 levels (about +10 and -10 V) to TTL voltage (0 and +5 V) and vice versa without requiring anything else than +5 V power supply. This chip contains two TTL->RS-232 and two RS-232->TTL drivers and needs four external 1 uF capacitors in order to generate the RS-232 voltage internally. The adapter electronic gets its power supply from the smartcard reader device VCC line or you can use an external 5 V supply if you wish.
The card slot's RST line is connected using one of the TTL->RS-232 drivers in the MAX232 to DCD, so that the software and the reader can easily resynchronize in case of a protocol error.
The I/O line is a bidirectional half-duplex asynchronous TTL level serial port.
We can connect this line to a MAX232 TTL input driver (which is connected to RxD and sends bytes to the PC) in order to receive data from the reader. The TxD signal is converted in the MAX232 to TTL level and is connected with an open collector TTL driver to I/O. This open collector...
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