W90P710_05 Datasheet, PDF (459/526 Pages) Winbond – 16/32-bit ARM microcontroller

W90P710
SCPSNT is tri-stated.
These I/O conditions also apply to socket in power down state (SCPWD = 1) or deselected socket in
idle state. Designers of application circuits must take extra care so that no contention occurs when
Smart Card interface is in those power-saving states.
z Active state
Active state is when Smart Card interface is actually performing all its functions: configuration of
control and interrupt registers, detection of card insertion/extraction, reception of ATR (Answer To
Reset) packet and communication of information between host and card. Refer to section 7.12.3 for
detailed function description.
This is the most power-consuming state and actual power consumption is dependent on traffic of
interface.
z Power down state
Transition from active state to power down state is accomplished by setting SCPWD to "1". Clock is
stopped for most internal core circuits except detection circuit for SCPSNT toggle (card
insertion/extraction). SCPSNT toggle can interrupt CPU and through this feature Smart Card interface
in power down state can be waken up by card insertion/extraction. User may also directly write a "0"
to SCPWD to wake up Smart Card interface.
Smart Card interface spends a little bit more power to maintain SCPSNT toggle detection circuit in
power down state than in disabled state while spares even more power than in active state by
stopping clock to core circuit.
Users must make sure that all on-going transactions are concluded before putting Smart Card
interface into power down state to prevent potential disoperation of internal state machine.
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Publication Release Date: January 17, 2005
Revision A.2