ISO 7816 Smart Card Standard

ISO 7816 Part 3: Electronic Signals and Transmission Protocols

This part describes electronic signals and transmission protocols of integrated circuit cards. We copied it from an older version that is available on the Internet. If you need the official version of this part, please contact ISO in Switzerland. If you have suggestions or material to include (tables, graphs etc) please contact us. The document will stay at this location for anyone that wants a direct link to this part of the standard. We will edit this document as necessary to bring it up to date and add comments.

Most of ISO7816-3 is important for reader manufacturers or developers who want to establish a communication with a smart card on a very low level (the signal level). Going through ISO 7816-3 you will see what’s involved in writing your own I/O software. This can be either to communicate from a microcontroller or a PC’s serial/parallel/USB/PCMCIA port. Even if you don’t go that far, it is interesting to read about what you can get out of an Answer to Reset (ATR).

For the latest version of ISO7816 part 3, please contact ISO in Switzerland.

There are many tools out there to read an ATR. Try HelloCard available at

Electrical Signals Description

I/O : Input or Output for serial data to the integrated circuit inside the card.

VPP : Programing voltage input (optional use by the card).

GND : Ground (reference voltage).

CLK : Clocking or timing signal (optional use by the card).

RST : Either used itself (reset signal supplied from the interface device) or in combination with an interal reset control circuit (optional use by the card). If internal reset is implemented, the voltage
supply on Vcc is mandatory.

VCC : Power supply input (optional use by the card).

NOTE – The use of the two remaining contacts will be defined in the appropriate application standards.

ISO7816 3.1 Voltage and current values


Vih : High level input voltage
Vil : Low level input voltage
Vcc : Power supply voltage at VCC
Vpp : Programming voltage at VPP
Voh : High level output voltage
Vol : Low level output voltage
tr : Rise time between 10% and 90% of signal amplitude
tf : Fall time between 90% and 10% of signal amplitude
Iih : High level input current
Iil : Low level input current
Icc : Supply current at VCC
Ipp : Programming current at VPP
Ioh : High level output current
Iol : Low level output current
Cin : Input capacitance
Cout: Output capacitance

* I/O

This contact is used as input (reception mode) or output (transmission mode) for data exchange. Two possible states exist for I/O:

– mark or high state (State Z), if the card and the interface device are in reception mode or if the state is imposed by the transmitter.

– space or low state (State A), if this state is imposed by the

When the two ends of the line are in reception mode, the line shall be maintained in state Z. When the two ends are in non-matced transmit mode, the logic state of the line may be indeterminate. During operations, the interface device and the card shall not both be in transmit mode.