DS_1217F_002
1.7.17.2 Answer to Reset Processing
73S1217F Data Sheet
A card insertion event generates an interrupt to the firmware, which is then responsible for the
configuration of the electrical interface, the UART and activation of the card. The activation sequencer
goes through the power up sequence as defined in the ISO 7816-3 specification. An asynchronous
activation timing diagram is shown in Figure 18. After the card RST is de-asserted, the firmware instructs
the hardware to look for a TS byte that begins the ATR response. If a response is not provided within the
pre-programmed timeout period, an interrupt is generated and the firmware can then take appropriate
action, including instructing the 73S1217F to begin a deactivation sequence. Once commanded, the
deactivation sequencer goes through the power down sequence as defined in the ISO 7816-3
specification. If an ATR response is received, the hardware looks for a TS byte that determines
direct/inverse convention. The hardware handles the indirect convention conversion such that the
embedded firmware only receives direct convention. This feature can be disabled by firmware within the
SByteCtl register. Parity checking and break generation is performed on the TS byte unless disabled by
firmware. If during the card session, a card removal, over-current or other error event is detected, the
hardware will automatically perform the deactivation sequence and then generate an interrupt to the
firmware. The firmware can then perform any other error handling required for proper system operation.
Smart card RST, I/O and CLK, C4, C8 shall be low before the end of the deactivation sequence. Figure
19 shows the timing for a deactivation sequence.
SELSC
bits
VCCSEL
bits
VCC
t4
VCCOK bit
RSTCRD bit
See Note
RST
CLK
ATR starts
IO
t1
t5
t4
t2
t3
tto
t1: SELSC.1 bit set (selects internal ICC interface) and a non-zero value in VCCSEL bits (calling for
a value of Vcc of 1.8, 3.0, or 5.0 volts) will begin the activation sequence. t1 is the time for Vcc to rise
to acceptable level, declared as Vcc OK (bit VCCOK gets set). This time depends on filter capacitor
value and card Icc load.
tto: The time allowed for Vcc to rise to Vcc OK status after setting of the VCCSEL bits. This time is
generated by the VCCTMR counter. If Vcc OK is not set, (bit VCCOK) at this time, a deactivation will
be initiated. VCCSEL bits are not automatically cleared. The firmware must clear the VCCSEL bits
before starting a new activation.
t2: Time from VCCTmr timeout and VCC OK to IO reception (high), typically 2-3 CLK cycles if
RDYST = 0. If RDYST = 1, t2 starts when VCCOK = 1.
t3: Time from IO = high to CLK start, typically 2-3 CLK cycles.
t4: Time allowed for start of CLK to de-assertion of RST. Programmable by the RLength register.
t5: Time allowed for ATR timeout, set by the STSTO register.
Note: If the RSTCRD bit is set, RST is asserted (low). Upon clearing RSTCRD bit, RST will be
de-asserted after t4.
Figure 18: Asynchronous Activation Sequence Timing
Rev. 1.2
81
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