DS8005 Datasheet, PDF (11/20 Pages) Maxim Integrated Products – Smart Card Intergace

Smart Card Interface
load current. Current to and from the card I/O lines is
limited internally to 15mA. The maximum frequency on
these lines is 1MHz.
Inactive Mode
The device powers up with the card interface in the
inactive mode. Minimal circuitry is active while waiting
for the host to initiate a smart card session.
• All card contacts are inactive (approximately 200Ω to
GND).
• The I/OIN pin in the high-impedance state (11kΩ
pullup resistor to V_DD).
• Voltage generators are stopped.
• XTAL oscillator is running (if included in the device).
• Voltage supervisor is active.
• The internal oscillator is running at its low frequency.
Activation Sequence
After power-on and the reset delay, the host microcon-
troller can monitor card presence with signals OFF and
CMDVCC, as shown in Table 2.
If the card is in the reader (if PRES_ is active), the host
microcontroller can begin an activation sequence (start
a card session) by pulling CMDVCC low. The following
events form an activation sequence (Figure 3):
1) CMDVCC is pulled low.
2) The internal oscillator changes to high frequency (t₀).
3) The voltage generator is started (between t₀ and t₁).
Table 2. Card Presence Indication
SEL_AB
Low
Low
High
High
SEL_AB
Low
Low
High
High
OFF
High
Low
High
Low
OFF2
High
Low
High
Low
CMDVCC
High
High
High
High
CMDVCC
High
High
High
High
STATUS
Card A present.
Card A not present.
Card B present.
Card B not present.
STATUS
Card B present.
Card B not present.
Card A present.
Card A not present.
CMDVCC
V_{CC_}
I/O_
ATR
CLK_
RSTIN
RST_
I/OIN
t₀ t₁
t₂
t₃
t₄
t₅ = t_ACT
Figure 3. Activation Sequence Using RSTIN and CMDVCC
______________________________________________________________________________________ 11