FPGA (Field Programmable Gate Array) as a programmable logic device has been widely used in various digital system designs, and the JTAG interface is one of the most commonly used debugging/programming interfaces. Its quality directly affects the performance and reliability of the FPGA. Therefore, it is essential to diagnose and test the JTAG to prevent FPGA failures. So how do we do this?
1. Working Principle of JTAG Interface
The JTAG interface is based on the IEEE 1149.1 standard, mainly used for boundary scanning and debugging of FPGAs. It transmits data serially and has the advantages of low cost and low power consumption. The JTAG interface mainly consists of signal lines such as TCK, TDI, TDO, and TMS, which allow access to and configuration of the internal logic of the FPGA.
2. Diagnosis and Testing of JTAG Interface
① Visual Inspection
First, check the appearance of the JTAG interface to ensure good connections without looseness or damage;
② Power Voltage Testing
Use a multimeter to measure the power voltage of the JTAG interface to ensure it meets the operating voltage range of the FPGA;
③ Signal Line Testing
Use an oscilloscope or logic analyzer to test the signal lines of the JTAG interface, checking the integrity, amplitude, and timing of the signals;
④ Boundary Scan Testing
Write a simple boundary scan testing program to access and configure the internal logic of the FPGA, observing whether the test results are correct;
⑤ Load Testing
Use the JTAG interface to load tests into the FPGA and check whether the program runs correctly;
⑥ Functional Testing
After the FPGA design is completed, perform functional testing to observe whether the system functions normally. If abnormalities occur, debugging and troubleshooting can be performed through the JTAG interface.
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