AT83C24B datasheet(21/42 Pages) ATMEL

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4234F–SCR–10/05

AT83C24

Table 7. CONFIG 1 (Config Byte 1)

ART

SHUTDOWN

CARDDET

PULLUP

CDS2

CDS1

CDS0

Bit

Number

Bit

Mnemonic

Description

This bit should not be set.

ART

Automatic Reset Transition

Set this bit to have the CRST pin changed according to activation sequence.

Clear this bit to have the CRST pin immediately following the value programmed

in CARDRST.

The reset value is 0.

SHUTDOWN

Shutdown

Set this bit to reduce the power consumption. An automatic de-activation

sequence will be done.

Clear this bit to enable VCARD[1:0] selection.

The reset value is 0.

CARDDET

Card Presence Detection Polarity

Set this bit to indicate the card presence detector is closed when no card is

inserted (CPRES is low).

Clear this bit to indicate the card presence detector is open when no card is

inserted (CPRES is high).Changing CARDDET will set INSERT bit (see

CONFIG0) even if no card is inserted or extracted.

The reset value is 0.

PULLUP

Pull-up Enable

Set this bit to enable the internal pull-up on the CPRES pin. This allows to

minimize the number of external components.

Clear this bit to disable the internal pull-up and minimize the power consumption

when the card detection contact is on. Then an external pull-up must be

connected to V

CC (typically a 1 MΩ resistor).

The reset value is 1.

2-0

CDS[2:0]

Card Detection filtering

CPRES is sampled by the master clock provided on CLK input. A change on

CPRES is detected after:

CDS[2-0] = 0: 0 sample

(1)

CDS[2-0] = 1: 4 identical samples

CDS [2-0] = 2: 8 identical samples (reset value)

CDS[2-0] = 3: 16 identical samples

CDS[2-0] = 4: 32 identical samples

CDS[2-0] = 5: 64 identical samples

CDS[2-0] = 6: 128 identical samples

CDS[2-0] = 7: 256 identical samples

The reset value is 2.

Note:

When CDS[2-0] = 0 and IT_SEL = 0, PRES/INT = 1 when no

card is present and PRES/INT = 0 when a card is inserted

even if CLK is STOPPED. This can be used to wake up the

external microcontroller and restart CLK when a card is

inserted in the AT83C24.

If CDS[2-0] = 0, IT_SEL = 1 and CLK is stopped, a card insertion or

extraction has no effect on PRES/INT pin.

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