AT83C24B-TIRIL ATMEL [ATMEL Corporation], AT83C24B-TIRIL Datasheet - Page 19

• Manufacturer Part Number: AT83C24B-TIRIL
• Description: Smart Card Reader Interface with Power Management
• Manufacturer: ATMEL [ATMEL Corporation]

Transparent Mode
Power Modes
4234G–SCR–01/07
If the microcontroller outputs ISO 7816 signals, a transparent mode allows to connect RST/CLK
and I/O/C4/C8 signals after an electrical level control. The AT83C24 level shifters adapt the card
signals to the smart card voltage selection.
The CRST and CCLK microcontroller signals can be respectively connected to the A1/RST and
A2/CK pins.
The CRST_SEL bit (in CONFIG4 register) selects standard or transparent configuration for the
CRST pin. CKS in CONFIG2 allows to select standard or transparent configuration for the CCLK
pin. So CCLK and CRST are independent. A2/CK to A0/3V inputs always give the TWI address
at reset. The A0/3V pin can be used for TWI addressing and easily connect two AT83C24
devices on the same TWI bus.
Two power-down modes are available to reduce the AT83C24 power consumption (see STUT-
DOWN bit in CONFIG1 register and LP bits in CONFIG3 register).
To enter in the mode number 4 (see Table 5), the sequence is the following:
The AT83C24 exits Power-down if a software/hardware reset is done or if SHUTDOWN bit is
cleared. The AT83C24 is then active immediately.
Either a hardware reset or a TWI command clearing the SHUTDOWN bit can cause an exit from
Power-down. The internal registers retain their value during the shutdown mode.
In Power-down mode, the device is sleeping and waiting for a wake up condition.
To reduce power consumption, the User should stop the clock on the CLK input after setting the
SHUTDOWN bit. The clock can be enabled again just before exiting SHUTDOWN (at least 10
µs before a START bit on SDA).
Figure 15. Transparent Mode Description
–
–
Microcontroller
First select the Low-power mode by setting the LP bit
The activation of the SHUTDOWN bit can then be done.
CCLK
CRST
CIO
CC4
CC8
A1/RST
A2/CK
I/O
C4
C8
AT83C24
CCLK
CRST
CIO
CC4
CC8
SMART CARD
AT83C24
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