ST8004 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'ST8004' PDF : 26 Pages View PDF
ST8004
Functional description
6.6
Inactive state
After power-on reset, the circuit enters the inactive state. A minimum number of circuits are
active while waiting for the microcontroller to start a session.
● All card contacts are inactive (approximately 200Ω to GND); I/OUC, AUX1UC and
AUX2UC are high impedance (10 kΩ pull-up resistor connected to VDD)
● Voltage generators are stopped
● XTAL oscillator is running
● Voltage supervisor is active
6.7
Activation sequence
After power-on and, after the internal pulse width delay, the microcontroller may check the
presence of the card with the signal OFF (OFF = HIGH while CMDVCC is High means that
the card is present; OFF = LOW while CMDVCC is HIGH means that no card is present).
If the card is in the reader (which is the case if PRES or PRES is true), the microcontroller
may start a card session by pulling CMDVCC LOW. The following sequence then occurs (see
Figure 5.):
● CMDVCC is pulled LOW (t0)
● The voltage doubler is started (t1~t0)
● VCC rises from 0 to 5 or 3V with a controlled slope (t2 = t1 +½3T)(I/O, AUX1 and AUX2
follow VCC with a slight delay); T is 64 times the period of the internal oscillator,
approximately 25µs
● I/O, AUX1 and AUX2 are enabled (t3 = t1 +4T)
● CLK is applied to the C3 contact (t4)
● RST is enabled (t5 = t1 +7T).
The clock may be applied to the card in the following way: set RSTIN High before setting
CMDVCC Low, and reset it Low between t3 and t5; CLK will start at this moment. RST will
remain LOW until t5, where RST is enabled to be the copy of RSTIN. After t5, RSTIN has no
further action on CLK. This is to allow a precise count of CLK pulses before toggling RST. If
this feature is not needed, then CMDVCC may be set LOW with RSTIN Low. In this case,
CLK will start at t3, and after t5, RSTIN may be set High in order to get the Answer To
Request (ATR) from the card.
6.8
Active state
When the activation sequence is completed, the ST8004 will be in the active state. Data are
exchanged between the card and the microcontroller via the I/O lines. The ST8004 is
designed for cards without VPP (this is the voltage required to program or erase the internal
non-volatile memory).
Depending on the layout and on the application test conditions (for example with an
additional 1pF cross capacitance between C2/C3 and C2/C7) it is possible that C2 is
polluted with high frequency noise from C3. In this case, it will be necessary to connect a
220pF capacitor between C2 and CGND.
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