ST7SCR datasheet(64/102 Pages) STMICROELECTRONICS

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ST7SCR

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SMARTCARD INTERFACE (Cont’d)

SMARTCARD CONTACT CONTROL REGISTER

(CRDCCR)

Read/Write

Reset Value: 00xx xx00 (xxh)

Note: To modify the content of this register, the LD

instruction must be used (do not use the BSET

and BRES instructions).

Bit 7 = CLKSEL

Card clock selection.

This bit is set and cleared by software.

0: The signal on the CRDCLK pin is a copy of the

CRDCLK bit.

1: The signal on the CRDCLK pin is a 4MHz fre-

quency clock.

Note: To start the clock at a known level, the CRD-

CLK bit should be changed before the CLKSEL

bit.

Bit 6 = Reserved, must be kept cleared.

Bit 5 = CRDC8

CRDC8 pin control.

Reading this bit returns the value present on the

CRDC8 pin. Writing this bit outputs the bit value on

the pin.

Bit 4 = CRDC4

CRDC4 pin control

Reading this bit returns the value present on the

CRDC4 pin. Writing this bit outputs the bit value on

the pin.

Bit 3 = CRDIO

CRDIO pin control.

This bit is active only if the UART bit in the CRDCR

present on the CRDIO pin.

If the UART bit is reset:

– Writing “0” forces a low level on the CRDIO pin

– Writing “1” forces the CRDIO pin to open drain

Hi-Z.

Bit 2 = CRDCLK

CRDCLK pin control

This bit is active only if the CLKSEL bit of the CRD-

CCR register is reset. Reading this bit returns the

value present in the register (not the CRDCLK pin

value).

When the CLKSEL bit is reset:

0: Level 0 to be applied on CRDCLK pin.

1: Level 1 to be applied on CRDCLK pin.

Note: To ensure that the clock stops at a given

value, write the desired value in the CRDCLK bit

prior to changing the CLKSEL bit from 1 to 0.

Bit 1 = CRDRST

CRDRST pin control.

Reading this bit returns the value present on the

CRDRST pin. Writing this bit outputs the bit value

on the pin.

Bit 0 = CRDVCC

CRDVCC Pin Control.

This bit is set and cleared by software and forced

to 0 by hardware when no card is present

(CRDIRF bit=0).

0: No voltage to be applied on the CRDVCC pin.

1: The selected voltage must be applied on the

CRDVCC pin.

Figure 37. Smartcard I/O Pin Structure

CLK

SEL

CRD

CLK

CRD

RST

CRD

VCC

I/O PIN

DATA BUS

CRDCCR

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