ACR39x – Reference Manual
Version 1.03
www.acs.com.hk
Page 8 of 35
5.0. Contact Smart Card Interface
The interface between the ACR39x and the inserted smart card follows the specification of ISO 7816-
3 with certain restrictions or enhancements to increase the practical functionality of ACR39x.
5.1. Smart Card Power Supply VCC (C1)
The current consumption of the inserted card must not be higher than 50 mA.
5.2. Programming Voltage VPP (C6)
According to ISO 7816-3, the smart card contact C6 (VPP) supplies the programming voltage to the
smart card. Since all common smart cards in the market are EEPROM-based and do not require the
provision of an external programming voltage, the contact C6 (VPP) has been implemented as a
normal control signal in the ACR39x. The electrical specifications of this contact are identical to those
of the signal RST (at contact C2).
5.3. Card Type Selection
The controlling computer must always select the card type through the proper command sent to the
ACR39x 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.
5.4. 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. Card Tearing Protection
The ACR39x provides a mechanism to protect the inserted card when it is suddenly withdrawn while it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 ACR39x 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: The ACR39x 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.
