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Sunday, March 17, 2019

ATR statistics: TA4

Article from the series "ATR statistics"


The first TA for T=15 encodes the clock stop indicator (X) and the class indicator (Y). The default values are X = "clock stop not supported" and Y = "only class A supported".

bits 8 and 7 indicate whether the card supports clock stop (≠ 00) or not (= 00) and, when supported, which state is preferred on the electrical circuit CLK when the clock is stopped.
  • 00b: Clock stop not supported
  • 01b: State L
  • 10b: State H
  • 11b: No preference

bits 6 to 1 indicate the classes of operating conditions accepted by the card. Each bit represents a class: bit 1 for class A, bit 2 for class B and bit 3 for class C.
  • 00 0001b: A only
  • 00 0010b: B only
  • 00 0100b: C only
  • 00 0011b: A and B
  • 00 0110b: B and C
  • 00 0111b: A, B and C
  • Any other value: RFU

200996.96 %
0x03271.30 %
0x83150.72 %
0xC3120.58 %
0x0760.29 %
0x4320.10 %
0xC710.05 %

Clock stop#%
not supported3352.38 %
state L23.17 %
state H1523.81 %
no preference1320.63 %

The class defines the current voltage the card can use:
  • class A: 5 V
  • class B: 3 V
  • class C: 1.8 V
Some readers can't provide a tension of 5V. For example the Gemalto CT1100 reader does only provide 3 V. The default value for TA4 is "only class A supported". Some (old) cards require a voltage of 5 V to work and will not work with a CT1100. That can be surprising.

A & B5688.89 %
A & B & C711.11 %