AN1978 - APPLICATION NOTE

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2. SEQUENCER

Core of the ST8004 is the sequencer (shown in figure 1) that must coordinate the enable signals for the

activation and deactivation sequence and check for possible fault conditions. This because the smart

card is basically a microcontroller and needs to be activated/deactivated by a correct sequence as

required by the ISO/IEC7816 standard.

Figure 2 and figure 3 show respectively the ST8004 activation and deactivation sequences.

Figure 2: Activation sequence

As shown in figure 2, when the PRES condition is true (PRES = low or PRES = high) and CMDVCC goes

last enabled signal is the RST that allows the start of the card software.

Figure 3 shows the deactivation sequence when the CMDVCC goes high. During the deactivation the I/O

outputs are deactivated at the time t13 being forced into a three-state condition, following the Vcc slope

(see CH 1 in figure 3).