How to connect a PC to a Videocrypt decoder

 


How to connect a PC to a Videocrypt decoder

-------------------------------------------


Markus Kuhn -- 1994-06-19



The easiest way to connect your PC to a Videocrypt pay-TV decoder is to

use the card slot as an interface and connect it with a voltage

converter (MAX232) and a TTL open collector driver (74LS07) to the

RS-232 serial port. This way, you don't even have to open the decoder

and the PC can now act as a smart card.


WARNING: In order to build the adapter described below, you will at

         least require some basic hobby electronics experience. If

         you don't understand, how the described circuitry works,

         better don't use it! Although the described procedure is

         relatively secure, serious errors might in the worst case

         damage both your PC and your TV system.


The chip cards used by the Videocrypt pay-TV system follow exactly the

specification ISO 7816 (you might find this international standard in a

good library, if you are interested in more details). 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 also be used in order to connect computers to

other 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.


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:



   ______________________________________

/                                        \

|                                          |

|                                          |

|    C1   C5                               |

|    C2   C6                               |

|    C3   C7                               |

|    C4   C8                               |

|                                          |

|                                          |

|                                          |

\________________________________________/




These contacts have the following purpose:



C1 VCC Supply voltage (+5 V, max. 200 mA)

C2 RST Reset signal

C3 CLK Clock signal

C4 - reserved

C5 GND Ground

C6 VPP Programming voltage (5-25 V)

C7 I/O Data input/output

C8 - reserved

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