Smart Card Interface

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9

When a card is inserted into the reader (if PRES is

active), the host microcontroller can begin an activation

sequence (start a card session) by pulling CMDVCC

low. The following events form an activation sequence

(Figure 3):

1) Host: CMDVCC is pulled low.

2) DS8024: The internal oscillator changes to high

3) DS8024: The voltage generator is started

× T). T is 64 times the

internal oscillator period (approximately 25µs).

6) DS8024: The CLK signal is applied to the C3 con-

An alternate sequence allows the application to control

when the clock is applied to the card.

1) Host: Set RSTIN high.

2) Host: Set CMDVCC low.

start.

the copy of RSTIN.

If the applied clock is not needed, set CMDVCC low

RSTIN can be set high to obtain an answer to request

(ATR) from an inserted smart card. Do not perform acti-

vation with RSTIN held permanently high.

Active Mode

When the activation sequence is completed, the

DS8024 card interface is in active mode. The host

microcontroller and the smart card exchange data on

the I/O lines.

ATR

CMDVCC

RST

RSTIN

CLK

I/O

I/OIN

Figure 3. Activation Sequence Using RSTIN and CMDVCC