ISO 7816 如何在读取 ATR 之前知道卡电压
[英]ISO 7816 How to know card voltage before reading ATR
问题描述
I know there are 3 types of contact cards.
我知道有 3 种类型的联系卡。 Class A,B,C (5V,3.3V,1.8V) A、B、C 类（5V、3.3V、1.8V）
I know we can get the voltage requirement of card from it's ATR.我知道我们可以从它的 ATR 获得卡的电压要求。
What I don't understand is how do we need to decide how many volts we need to feed the card just before the card's Atr information is read?我不明白的是，在读取卡的 Atr 信息之前，我们如何确定需要为卡供电的电压是多少？
1 个解决方案
解决方案1
0 2022-05-15 10:33:34
No, the voltage class is not typically encoded in the ATR (even if nobody restricts to put it into the historical bytes), since if you are able to read the ATR you are obviously applying an acceptable voltage.不，电压等级通常不会在 ATR 中编码（即使没有人限制将其放入历史字节中），因为如果您能够读取 ATR，您显然是在施加可接受的电压。
The process for a reader is, to apply the lowest voltage, and if the card does not react, try the next voltage.读卡器的过程是，施加最低电压，如果卡没有反应，则尝试下一个电压。 See this question on electrical engineering.请参阅有关电气工程的这个问题。
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