w83637hg Winbond Electronics Corp America, w83637hg Datasheet - Page 100

• Manufacturer Part Number: w83637hg
• Description: Winbond Lpc I/o Lpc I/o
• Manufacturer: Winbond Electronics Corp America

W83637HF/HG
To meet another timing requirement, tc of ISO/IEC 7816-3, a counter based on SCCLK is implemented
to start counting on the rising edge of SCRST#. SCPWR# is deactivated if no ATR (Answer To Reset)
is detected after 65536 clock cycles from the rising edge of SCRST#.
7.7 Answer-to-Reset
Answer-to-Reset (ATR) is the data streams sent by the card to the interface as an answer to a reset on
SCRST# signal. Refer to ISO/IEC 7816-3 for detailed description of ATR.
There're two kind of cards specified in ISO/IEC 7816-3, inverse convention card and direct convention
card. Although these two conventions treat logical meanings (0 or 1) of voltage levels (low or high)
differently, Winbond's implementation of Smart Card interface decodes a high voltage level data bit as
"1" and low voltage level data bit "0" nevertheless and resorts to software to interpret incoming data.
Software driver needs to interpret initial character of ATR first to determine which convention is for
inserted card and chooses a conversion procedure for it. Subsequent incoming data bytes must be
passed through a conversion procedure before actually transfers these data bytes to host. Similar
conversion procedure must be applied to outgoing data byte before writing to TBR too.
For example, the raw data byte for initial character of inverse-convention ATR would be 03h.
Software driver therefore needs a conversion procedure to reverse bit-significance and polarity to
process subsequent raw data bytes. On the other hand, initial character of direct-convention ATR is
3Bh which needs no conversion procedure to process data byte.
7.8 Data Transfer
Software driver might need to configure control registers again based on information contained in ATR
before process subsequent data transfer. The following guidelines are provided for programming
reference.
1. EPE should be set to "1" for direct-convention card and otherwise for inverse-convention card.
2. BLH, BLL and CBR should be set to comply with Fi and Di.
3. GTR is used for various stop bit requirement of different transmission protocols.
4. SCIODIR controls direction of data transfer.
5. Use interrupt resources to control communication sequence.
6. Monitor SCSR for transmission integrity.
7.9 Cold Reset and Warm Reset
Cold reset is achieved by writing a "1" to bit 7 of ECR. It deactivates SCPWR# to high.
Consequentially, SCRST# is pulled down and SCCLK is stopped. User must write a "0" to ECR bit 7 to
resume Smart Card interface to a normal activation state as described in section 2.3.2 assuming card
is still present.
Writing a "1" to ECR bit 0 triggers a warm reset. This is a self-cleared reset operation unlike cold reset
which needs explicit cancellation. Its effect is similar to cold reset except SCPWR# is kept activated
and therefore power supply to card stays on.
Publication Release Date: March, 2006
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Revision 1.6