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很多不同的器件和应用都包含一个n位串行到并行移位器这样一个公用电路单元(图1)。通过串行连接发送数据在接收端需要这种类型的电路。当测试这种器件的工作时,应提供串行数据,同时把串行数据看作n位数组时,串行数据包含0和1的所有2~n可能的数据组合。这就可保证,对移位器并行输出的逻辑响应在所有的条件下都是正确的。另外,这种串行数据流应尽可能的短,以节省测试时间。一种办法是:在(2~n×n)位串行数据流中不设置n位的所有2~n数组,而是在n-1初始化位之后在最佳的2~n位中实现。当n等于4时,下面的0和1的数据申包含4位的所有16种组合:
Many different devices and applications include an n-bit serial-to-parallel shifter such a common circuit unit (Figure 1). Sending data over a serial connection requires this type of circuitry at the receiving end. When testing the operation of such a device, serial data should be provided and at the same time as serial data is treated as an n-bit array, the serial data contains all possible 2-to-n data combinations of 0 and 1. This ensures that the logic response to the shifter’s parallel output is correct under all conditions. In addition, this serial data stream should be as short as possible to save test time. One approach is to not set all 2-n arrays of n bits in a serial data stream of (2~n × n) bits, but in the optimal 2~n bits after the n-1 initialization bits. When n is equal to 4, the data below 0 and 1 contain all 16 combinations of 4 bits: