Smart Card Interface

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7

Pin Description

PIN

NAME

FUNCTION

1, 2

CLKDIV1,

CLKDIV2

Clock Divider. Determines the divided-down input clock frequency (presented at XTAL1 or from a

crystal at XTAL1 and XTAL2) on the CLK_ output pin. Dividers of 1, 2, 4, and 8 are available.

3

5V/3V

5V/3V Selection Pin. Allows selection of 5V or 3V for communication with an IC card. Logic-high

selects 5V operation; logic-low selects 3V operation. The 1_8V pin overrides the setting on this pin if

active. See Table 3 for a complete description of choosing card voltages.

4

1_8V

1.8V Operation Selection. This active-high input puts the device into 1.8V smart card communication

mode. The selected interface (when activated) powers a card with a 1.8V supply and all I/O lines

operate at 1.8V.

5

Smart Card Supply Voltage, Interface B. Decouple to CGND (card ground) with 2 x 100nF or 100 +

200nF capacitors (ESR < 100m ).

6

Smart Card Interface Supply. 5V power supply for powering the card interface.

7

RSTB

Smart Card Reset, Interface B. Card reset output from contact C2.

8

CLKB

Smart Card Clock, Interface B. Card clock, contact C3.

9, 14

CGND

Smart Card Ground

10

PRESA

Interface A Card Presence Indicator. Active-high card presence input for the first card interface.

When the presence indicator becomes active, a debounce timeout begins. After 8ms (typ), the OFF

signal becomes active if the first card interface is selected (SEL_AB low), else the OFF2 signal

becomes active.

11

I/OA

Smart Card Data-Line Output, Interface A. Card data communication line, contact C7. This pin is

only active if the first card interface is selected (SEL_AB low) and the interface has gone through an

activation sequence.

1_8V

28

27

26

25

24

23

22

SEL_AB

OFF2

I/OIN

XTAL2

TOP VIEW

XTAL1

OFF

GND

20 RSTIN

19 CMDVCC

16 RSTA

15 CLKA

5V/3V

CLKDIV2

CLKDIV1

RSTB

CLKB

CGND

PRESA

I/OA

I/OB

PRESB

4

1

2

3

5

6

7

8

9

10

11

12

13

14

CGND

SO

DS8005

Pin Configuration