TDA8030 datasheet(26/57 Pages) PHILIPS

26 / 57 page

2003 Jul 04

Philips Semiconductors

Product speciﬁcation

USB smart card reader (OTP or ROM)

TDA8030; TDA8031

Table 24 Description of the CCR bits

Table 25 CLK value for an asynchronous card

Note

1. If fCLK =fXTAL, the duty cycle must be ensured by the incoming clock signal on XTAL1.

BIT

SYMBOL

DESCRIPTION

−

not used

−

not used

SHL

Stop HIGH or LOW: If bit CST = 1, then the clock is stopped at LOW level if SHL = 0

and at HIGH level if SHL = 1. In these modes, the bias current in the card drivers is

reduced; the current drawn by the card (ICC) should be less than 10 mA at all VCC

voltages.

CST

Clock stop: In case of asynchronous cards, bit CST deﬁnes whether the clock to the

card is stopped or not. If bit CST is reset, then the clock is determined by bits AC0,

AC1 and AC2; see Table 25. All frequency changes are synchronous, thus ensuring

that no spike or unwanted pulse widths occurs during changes.

Synchronous Clock: In the event of synchronous cards, the clock contact is a copy of

the value written in SC. In reception mode, the data from the card is available in bit UR0

after a read operation of the URR register. In transmission mode, bit UT0 is written on

the I/O line of the card when UTR register has been written.

2 to 0

AC2 to AC0

When switching from 1

⁄nfxtal to 1⁄2fint or vice versa, only bit AC2 must be changed;

AC1 and AC0 must remain the same. When switching from 1

⁄nfxtal or 1⁄2fint to CLK STOP

or vice versa, only bits CST and SHL must be changed.

When switching from 1

⁄nfxtal to 1⁄2fint or vice versa, a maximum delay of 200 µs can occur

between the command and the effective frequency change on pin CLK. The fastest

switch is from 1

⁄2fxtal to 1⁄2fint or vice versa, the best duty cycle is from 1⁄8fxtal to 1⁄2fint or

vice versa. The status bit CLKSW within the MSR gives the effective switch moment.

AC2

AC1

AC0

CLK(1)

000

fxtal

001

⁄2fxtal

010

⁄4fxtal

011

⁄8fxtal

100

⁄2fint

101

⁄2fint

110

⁄2fint

111

⁄2fint

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