73S8023C Data Sheet
DS_8023C_019
8.4 Deactivation Sequence (Asynchronous Mode)
Deactivation is initiated either by the system controller by setting CMDVCC high, or automatically in the
event of hardware faults. Hardware faults are over-current, overheating, VDD fault, VCC fault, and card
extraction during the session.
The following steps list the deactivation sequence and the timing of the card control signals when the
system controller sets the CMDVCC high or OFF goes low due to a fault or card removal:
1. RST goes low at the end of time t1.
2. CLK stops low at the end of time t2.
3. I/O goes low at the end of time t3. Out of reception mode.
4. VCC is shut down at the end of time t4. After a delay t5 (discharge of the VCC capacitor), VCC is low.
CMDVCC
-- OR --
OFF
RST
CLK
I/O
VCC
t3
t4
t2
t5
t1
t1 ≥ 0.5 µs, timing by 1.5 MHz internal Oscillator
t2 ≥ 7.5 µs
t3 ≥ 0.5 µs t4 ≥ 0.5 µs
t5 = depends on VCC filter capacitor.
t1 + t2 + t3 + t4 + t5 ~= 100 µs
Figure 7: Asynchronous Deactivation Sequence
9 OFF and Fault Detection
There are two cases for which the system controller can monitor the OFF signal: to query regarding the
card presence outside card sessions, or for fault detection during card sessions.
Monitoring Outside a Card Session
In this condition, CMDVCC is always high, OFF is low if the card is not present, and high if the card is
present. Because it is outside a card session, any fault detection will not act upon the OFF signal. No
deactivation is required during this time.
Monitoring During a Card Session
CMDVCC is always low, and OFF falls low if the card is extracted or if any fault is detected. At the same
time that OFF is set low, the sequencer starts the deactivation process.
Figure 8 shows the timing diagram for the signals CMDVCC, PRES, and OFF during a card session and
outside the card session:
14
Rev. 1.5
TERIDIAN [ TERIDIAN SEMICONDUCTOR CORPORATION ]
