DS8005 データシートの表示（PDF） - Maxim Integrated

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DS8005

Smart Card Interface

Maxim Integrated 

DS8005

Smart Card Interface

Switching A/B Interfaces

One of the device’s key features is the ability to manage

two card slots at the same time. The multiplexing control

signal SEL_AB is used to determine which interface is

active for communication, though it is possible to leave

both interfaces powered at the same time.

When switching between interfaces, the device preserves

the state of control signals CLKDIV1, CLKDIV2, 1.8V,

5V/3V, CMDVCC, and RSTIN by latching the pin states.

This allows the now inactive interface to stay powered

while the other interface is activated for communication,

and it also allows for fast switching between card interfaces

without the need for a card deactivation and activation

sequence.

When switching interfaces, the host must reset the con-

trol pins in the same configuration that was last used

for that interface. Approximately 78µs after the SEL_AB

transition, the device compares its internal state for the

selected interface to the present state of the control pins.

If the present state of the control pins does not match the

previously latched state, the device does not perform the

switchover correctly and enters an un­known state. This

means that the host must always record the state of the

control pins for the current interface before performing a

switchover.

1_8V, 5V/3V, CLKDIV1,

CLKDIV2, RST, I/O

SEL_AB

TRANSITION

SENSOR

DELAY

OFF

OFF2

Figure 10. Switching A/B Interfaces

TRANSPARENT

LATCH A

ENA

REG A

CLKA DIV

TRANSPARENT

LATCH B

ENA

1

0

1

0

REG B

CLKB DIV

SMART CARD

STATUS 1

SMART CARD

STATUS 2

DS8005

VCCA

CLKA

RSTA, I/OA, GNDA

VCCB

CLKB

RSTB, I/OB, GNDB

PRESA

PRESB

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