ncn6004a ON Semiconductor, ncn6004a Datasheet - Page 20

• Manufacturer Part Number: ncn6004a
• Description: Dual Sam/sim Interface Integrated Circuit
• Manufacturer: ON Semiconductor

CARD DETECTION
The card detector circuit provides a constant low current to
bias the CRD_DET_A and CRD_DET_B pins, yielding a
logic High when no card is present and the external switch is
Normally Open type. The internal logic associated with pins
20 and 41 provides a programmable selection of the slope
card detection. The transition is filtered out by the internal
digital filter circuit, avoiding false interrupt. In addition to
the typical 50 ms delay, the MPU shall provide an additional
delay to cope with the mechanical stabilization of the card
interface (typically 1 ms), prior to valid the CRD_VCC_A or
CRD_VCC_B supply.
going slope on the Chip Select pin as depicted in Figure 11,
or by forcing the PWR_ON signal High (keeping CS = Low)
for the related card.
*The polarity change is validated upon the next positive PGM transient.
Table 5. Card Detection Polarity
The interrupt signal can be cleared either by a positive
CS
1
0
0
0
0
0
CLEAR INTERRUPT
CARD PRESENT: STATUS = 1
CLEAR INTERRUPT
CARD NOT PRESENT: STATUS = 0
CRD_DET_A
CARD_SEL
PGM
X
1
0
0
0
0
STATUS
PGM
INT
CS
A0
A1
A2
A3
A3
X
X
1
1
1
1
ACKNOWLEDGE
INTERRUPT
A2
X
X
1
1
1
1
50 ms < T < 150 ms
A1
X
X
0
0
0
0
Figure 11. Typical Interrupt Sequence
A0
X
X
0
1
0
1
CARD IDENTIFICATION
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& PROCESSING
NCN6004A
CARD_SEL
20
X
X
1
1
0
0
INT = Low as depicted before, the external mP being
responsible to clear the interrupt signal, taking the
necessaries actions. When the NCN6004A detects a card
extraction, the power down sequence is automatically
activated for the related interface section, regardless of the
PWR_ON state, and the INT pin is asserted Low. It is up to
the external MPU to clear this interrupt by pulsing the CS
pin.
The polarity of the card detection switch can be either
Normally Open or Normally Close and is software
controlled as defined here below and in Table 2.
When a card is inserted, the detector circuit asserts
Normally Close
Normally Open
CRD_DET_A
CARD EXTRACTED
Qn −1
Qn −1
Qn −1
Bn −1
50 ms < T < 150 ms
High
High
High
IRRELEVANT
IRRELEVANT
High = Card A
Normally Close
Normally Open
CRD_DET_B
Qn −1
Qn −1
Qn −1
Qn −1