AT83C24B datasheet(9/42 Pages) ATMEL

9 / 42 page

4234F–SCR–10/05

AT83C24

Read Command

After the slave address has been configured, the read command allows to read one or several

bytes in the following order:

•

STATUS, CONFIG0, CONFIG1, CONFIG2, CONFIG3, INTERFACE, TIMER1, TIMER0,

CAPTURE1, CAPTURE0

•

FFh is completing the transfer if the microcontroller attempts to read beyond the last byte.

Note:

Flags are only reset after the corresponding byte read has been acknowledged by the master.

Table 4. Read Command Description

Interrupts

The PRES/INT behavior depends on IT_SEL bit value (see CONFIG4 register).

•

If IT_SEL= 0, the PRES/INT output is High by default (on chip pull up or open drain).

PRES/INT is driven Low by any of the following event:

–

INSERT bit set in CONFIG0 register (card insertion/extraction or bit set by software )

–

VCARD_INT bit set in STATUS register (the DC/DC output voltage has settled)

–

over-current detection on CVCC

–

VCARDERR bit set in CONFIG0 register (out of range voltage on CVCC or bit set by

software)

–

ATRERR bit set in CONFIG0 register (no ATR before the card clock counter

overflows or bit set by software).This control of ATR timing is only available if ART bit

=1.

If IT_SEL=0, a read command of STATUS register and of CONFIG0 register will release

PRES/INT pin to high level.

Several AT83C24 devices can share the same interrupt and the microcontroller can identify

the interrupt sources by polling the status of the AT83C24 devices using TWI commands.

•

If IT_SEL= 1 (mandatory for NDS applications and for software compatibility with existing

devices) the PRES/INT output is High to indicate a card is present and none of the following

event has occured:

Byte Description

Byte Value

Address byte

0100 A

2A1A01

Data byte 1

STATUS

Data byte 2

CONFIG0

Data byte 3

CONFIG1

Data byte 4

CONFIG2

Data byte 5

CONFIG3

Data byte 6

CONFIG4

Data byte 7

INTERFACE

Data byte 8

TIMER 1 (MSB)

Data byte 9

TIMER 0 (LSB)

Data byte 10

CAPTURE 1 (MSB)

Data byte 11

CAPTURE 0 (LSB)

Data byte 12

0xFF

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