Detection of initial chip state (distinguish case "no PCF connected" and "PCF in protected mode")

[tusker-tools]

When performing the first communication (connect mdi command) with a PCF79xx transponder chip, several failure situations are possible:

• No PCF connected (PCF not conncted at all, wires have no contact)
• PCF is in protected mode (resulting signal characteristic could be differ from kind of PCF chip, e.g. PCF7945 different from 26A0700)

Depending on the error, the user must draw the corresponding counter-measure (check wire connections / delete chip).
Therefore, the tool must detect and distinguish between the different errors and feedback related information to the user.

[tusker-tools]

Enhancement successfully tested with PCF7945 CAS3 BMW key (5WK49125).

Test necessary for 26A0700 type transponder (@Schtani )

[tusker-tools]

For 26A0700 china transponder, situation "PCF protected" and "PCF not properly connected" was not distinguished properly.
This is fixed with 3e21de5

[tusker-tools]

Final test necessary by Schtani