一种JTAG电路的实现及仿真

Realization and Simulation of JTAG Circuit

JTAG是一种电路的测试协议,广泛应用于集成电路的测试。随着JTAG技术的发展,它已经不局限于对电路的测试,越来越多复杂的可编程电路都支持JTAG配置电路的方式。介绍一种JTAG电路,具体分析了电路整体结构以及三个组成部分,分别为TAP控制器、指令寄存器和边界扫描单元。TAP控制器是电路控制的核心部分,它是一个16位的状态机电路,指令寄存器和边界扫描单元由触发器和锁存器以及多路选择器组成。利用NC-verilog软件对电路的三个部分及指令进行了数字仿真,TAP控制器依照JTAG标准给出的状态跳转进行仿真,结果和JTAG标准中一致,指令寄存器和边界扫描单元电路仿真结果也符合功能要求,从而验证了设计中提出的JTAG电路的功能正确性。

JTAG,as a test agreement of circuit,is widely used in the test of integrated circuit. With the development of JTAG technique,JTAG is not only used to test circuit,but it also supports complex programmable circuit. This paper introduces a JTAG circuit,concretely analyzes the whole structure and three parts of JTAG circuit which are TAP controller,instruction register and BSR cell. TAP controller,the core part in the circuit,is a 16 bit state machine circuit,and instruction register and BSR cell are composed of DFF,LATCH and MUX. NC- verilog is used to simulate the three parts and instructions of JTAG circuit,TAP controller is simulated according to the state jumping given by JTAG standard,the result is same as JTAG one and the simulation result of instruction register and BSR cell comply with the function request,consequently,the correction of the JTAG circuit functions is verified.