ST8024

Functional description

17/30

5.5

Inactive mode

After a Power-on reset, the circuit enters the inactive mode. A minimum number of circuits

are active while waiting for the microcontroller to start a session:

– All card contacts are inactive (approximately 200

Ω to GND)

– Pins I/OUC, AUX1UC and AUX2UC are in the high-impedance state (11 k

Ω pull-up

– Voltage generators are stopped

– XTAL oscillator is running

– Voltage supervisor is active

– The internal oscillator is running at its low frequency.

5.6

Activation sequence

After power-on and after the internal pulse width delay, the system microcontroller can

check the presence of a card using the signals OFF and CMDVCC as shown in

Table 21.

If the card is in the reader (this is the case if PRES or PRES is active), the system

microcontroller can start a card session by pulling CMDVCC LOW. The following sequence

then occurs (see

Figure 6.):

64 times the period of the internal oscillator (approximately 25 µs).

moment).

The clock may be applied to the card using the following sequence (see Fig.5):

1. Set RSTIN HIGH.

2. Set CMDVCC LOW.

pulses before toggling RST.

If the applied clock is not needed, then CMDVCC may be set LOW with RSTIN LOW. In this

may be set HIGH in order to obtain an Answer To Request (ATR) from the card.

Activation should not be performed with RSTIN held permanently HIGH

Table 21.

Card presence indicator

OFF

CMDVCC

Indication

H

H

card present

L

H

card not present