ACR3901U-S1 – Reference Manual
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Version 1.09
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Page 13 of 96
5.5.3. Card Type Selection
The controlling computer must always select the card type through the proper command sent to the
ACR3901U-S1 prior to activating the inserted card. This includes both the memory cards and MCU-
based cards.
For MCU-based cards, the reader allows to select the preferred protocol, T=0 or T=1. However, this
selection is only accepted and carried out by the reader through the PPS when the card inserted in
the reader supports both protocol types. Whenever an MCU-based card supports only one protocol
type, T=0 or T=1, the reader automatically uses that protocol type, regardless of the protocol type
selected by the application.
5.5.4. Interface for Microcontroller-based Cards
For microcontroller-based smart cards, only the contacts C1 (VCC), C2 (RST), C3 (CLK), C5 (GND)
and C7 (I/O) are used. A frequency of 4.8 MHz is applied to the CLK signal (C3).
5.5.5. Card Tearing Protection
The ACR3901U-S1 provides a mechanism to protect the inserted card when it is suddenly withdrawn
while it is powered up. The power supply to the card and the signal lines between the ACR3901U-S1
and the card is immediately deactivated when the card is being removed.
However, as a rule to avoid
any electrical damage, a card should only be removed from the reader while it is powered down.
Note: ACR3901U-S1 never switches on the power supply to the inserted card by itself. The
controlling computer through the proper command sent to the reader must explicitly do this.
