DS8005 Datasheet, PDF (8/20 Pages) Maxim Integrated Products – Smart Card Intergace

Smart Card Interface
PIN
12
13
15
16
17
18
19
20
21
22
23
24, 25
26
27
28
Pin Description (continued)
NAME
I/OB
PRESB
CLKA
RSTA
V_CCA
V_DDA2
CMDVCC
RSTIN
V_DD
GND
OFF
XTAL1,
XTAL2
I/OIN
OFF2
SEL_AB
FUNCTION
Smart Card Data-Line Output, Interface B. Card data communication line, contact C7. This pin is
only active if the second card interface is selected (SEL_AB high) and the interface has gone
through an activation sequence.
Interface B Card Presence Indicator. Active-high card presence input for the second card interface.
When the presence indicator becomes active, a debounce timeout begins. After 8ms (typ), the OFF
signal becomes active if the second card interface is selected (SEL_AB high), else the OFF2 signal
becomes active.
Smart Card Clock, Interface A. Card clock, contact C3.
Smart Card Reset, Interface A. Card reset output from contact C2.
Smart Card Supply Voltage, Interface A. Decouple to CGND (card ground) with 2 x 100nF or 100 +
220nF capacitors (ESR < 100m
).
Smart Card Interface Supply. 5V power supply for powering the card interface. While this pin is not
required to be connected to 5V (it can be left not connected (N.C.)), it is recommended for the best
performance when delivering power to a 5V smart card.
Activation Sequence Initiate. Active-low input from host.
Card Reset Input. Reset input from the host.
Supply Voltage
Digital Ground
Status Output for Selected Interface. Active-low interrupt output to the host. Includes a 20k

integrated pullup resistor to V_DD. This pin reflects fault events and PRES_ events on the currently
selected interface only (behaving as if it were a DS8024 with only one interface). The OFF2 pin
should be used to monitor presence events on the nonselected interface.
Crystal/Clock Input. Connect an input from an external clock to XTAL1 or connect a crystal across
XTAL1 and XTAL2.
I/O Input. Host-to-interface chip data I/O line.
Status Output for Nonselected Interface. This pin passes through the presence signal for the
nonselected interface. If SEL_AB is low (the A interface is selected), this pin reflects the state of the
PRESB input. If SEL_AB is high (the B interface is selected), this pin reflects the state of the PRESA
input.
Interface Selection. This pin selects the interface the input pins (I/OIN, RSTIN, etc.) communicate
with and control. If SEL_AB is low, the A interface is selected. Activation sequences power up V_CCA
and communication occurs with CLKA, I/OA, and RSTA. If SEL_AB is high, the B interface is
selected. Both interfaces can be powered and clocking at the same time. See the Switching A/B
Interfaces section for more information.
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