AT83C24NDS-PRRUM ATMEL [ATMEL Corporation], AT83C24NDS-PRRUM Datasheet - Page 10

• Manufacturer Part Number: AT83C24NDS-PRRUM
• Description: Smart Card Reader Interface with Power Management
• Manufacturer: ATMEL [ATMEL Corporation]

Card Presence Detection
10
Figure 4. Card Presence Input
VCC
VCC
VSS
VSS
AT83C24
Card
Contact
Presence
Card
Contact
External
Pull-down
External
Pull-up
Presence
The card presence is provided by the CPRES pin. The polarity of card presence contact is
selected with the CARDDET bit (see CONFIG1 register). A programmable filtering is controlled
with the CDS[2-0] bits (see CONFIG1 register).
An internal pull-up on the CPRES pin can be disconnected in order to reduce the consumption,
an external pull-up must then be connected to VCC. The PULLUP bit (see CONFIG1 register)
controls this feature.
The card presence switch is usually connected to Vss (card present if CPRES=1). The CARD-
DET bit must be set. The internal pull up can be connected.
If the card presence contact is connected to Vcc (card present if CPRES=0), the internal pull-up
must be disconnected (see PULLUP bit) and an external pull-down must be connected to the
CPRES pin.
An interrupt can be generated if a card is inserted or extracted (see interrupts §).
PRES/INT
–
–
CPRES
over-current detection on CVCC
VCARDERR bit set in CONFIG0 register (out of range voltage on CVCC or bit set by
software)
Internal
Pull-up
EVCC
(See Table 18)
VCC
INT_PULLUP Bit
= 1 Closed
= 0 Open
PULLUP Bit
IT Controller
= 1 Closed
= 0 Open
IT_SEL Bit
CARDDET Bit
= 1 No Card if CPRES = 0
= 0 No Card if CPRES = 1
FILTERING
CDS[2-0]
= 1 Card Inserted
= 0 No Card
CARDIN bit
4234F–SCR–10/05