Based on the jointed test action group ( JTAG) protocol, instructions and scan chain were introduced. With test access port ( TAP) module exchanging serial input with parallel output, register files and random access memory on chip were read or written in parallel. 在JTAG接口协议的基础上,增加指令和扫描链,同时通过测试访问端(TAP)控制把串行输入转换成并行输出,并行访问数字信号处理器的寄存器文件和片上存储器单元,实现嵌入式模拟器。