ATR statistics: TD3 - Structural, encodes Y4 and T

Article from the series "ATR statistics"

TD3 - Structural, encodes Y4 and T

The ISO 7816-3 specification is not public. So I can't copy/paste part of the text. I will use Wikipedia instead.

Refer to TD1 - Structural, encodes Y2 and T since the definition of TD₃ is identical to TD₁.

TD3	#	%
	2009	96.96 %
0x1F	61	2.94 %
0x3F	2	0.10 %

TD₃ (as the other TD_i bytes) is structural and indicates:

• How to interpret the other ATR bytes
• What communication protocol the card wants to use

For 96.96% of the ATRs no TD₃ is present. So no other TA₄, TB₄, TC₄ or TD₄ is present and no new protocol is defined so the protocol(s) defined by TD₁ and TD₂ will be used.

For 2.94% of the ATRs TD₃ = 0x1F. The high nibble is 0001b so TA₄ is present and T=15 protocol is defined. One such ATR is 3B 94 18 81 B1 80 7D 1F 03 19 C8 00 50 DC.

For 0.10% of the ATRs TD₃ = 0x3F. The high nibble is 0001b so TA₄ and TB₄ are present and T=15 protocol is defined. One such ATR is 3B DE 18 FF 81 F1 FE 43 00 3F 07 83 44 45 53 46 69 72 65 38 20 53 41 4D 2D 58 17.