Smart Card Interface

6

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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. See Table 3 for a complete description of choosing card

voltages.

4

PGND

Analog Ground

5, 7

CP2, CP1

Step-Up Converter Contact. Charge-pump capacitor. Connect a 100nF capacitor (ESR < 100m )

between CP1 and CP2.

6

8

9

PRES

Card Presence Indicator. Active-low card presence inputs. When the presence indicator becomes

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

10

PRES

Card Presence Indicator. Active-high card presence inputs. When the presence indicator becomes

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

11

I/O

Smart Card Data-Line Output. Card data communication line, contact C7.

12, 13

AUX2,

AUX1

Smart Card Auxiliary Line (C4, C8) Output. Data line connected to card reader contacts C4 (AUX1) and

C8 (AUX2).

14

CGND

Smart Card Ground

15

CLK

Smart Card Clock. Card clock, contact C3.

16

RST

Smart Card Reset. Card reset output from contact C2.

17

Smart Card Supply Voltage. Decouple to CGND (card ground) with 2 x 100nF or 100 + 220nF

capacitors (ESR < 100m ).

18

N.C.

No Connection. Unused on the DS8024.

19

CMDVCC

Activation Sequence Initiate. Active-low input from host.

20

RSTIN

Card Reset Input. Reset input from the host.

21

Supply Voltage

22

GND

Digital Ground

23

OFF

Status Output. Active-low interrupt output to the host. Use a 20k

24, 25

XTAL1,

XTAL2

Crystal/Clock Input. Connect an input from an external clock to XTAL1 or connect a crystal across

XTAL1 and XTAL2. For the low idle-mode current variant, an external clock must be driven on XTAL1.

26

I/OIN

I/O Input. Host-to-interface chip data I/O line.

27, 28

AUX1IN,

AUX2IN

C4/C8 Input. Host-to-interface I/O line for auxiliary connections to C4 and C8.