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从前在“设计思路”栏目下发表的“简单的PC智能卡阅读器”(请参见本刊1996年第8期99页)可以加以改进,其方法是要把PC并行数据口备用线的电流输出能力考虑进去.这些信号线有足够的电流能力为智能卡访问器供电而不需要外接电源(见图).另外一个好处是,原文中所列的软件表不用修改就可以使用,这是因为在原来程序中由缺省值把PC并行口的不同的五条数据线设计为高态.如图所示,当这些信号线用五个通用二极管并行连接时,将会使PC打印机口逻辑的内部V_(CC)电源也可给读出的智能卡供
The “simple PC smart card reader” previously published under “Design Ideas” (see Issue 8, 1996, p. 99) can be improved by putting the current output capability of the PC parallel data port back-up line The signal lines have enough current capability to power the smart card accessors without the need for an external power supply (see figure) Another benefit is that the software listings listed in the original text can be used without modification, since in the original program By default, the different five data lines of the PC parallel port are designed to be high, as shown in the figure, when these signal lines are connected in parallel with five general purpose diodes, the internal V_ (CC Power can also be read out for the smart card