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Introduction
Whether it is customer feedback or your own experience, USB-blaster cannot download and configure FPGA from time to time. The reasons are as follows:
1. The JTAG-related pins on FPGA Devices are faulty;
2. the USB-blaster is broken;
3. The 10-pin JTAG cable is not properly pressed.
Among them, Article 1 has brought the most serious damage to us. How should we avoid it?
Content fault 1
TCK, TMS, TDO, or TDI of the JTAG interface, short-circuited with Gnd.
Cause Analysis
For the convenience of graphs, we often plug and unplug the JTAG download port without charge. Although the JTAG-related pins are safe and sound in most cases, it cannot avoid small probability events: static electricity and Surges Caused by hot swapping will penetrate through the JTAG-related pins. Some people speculate that this type of fault occurs only when pirated USB-blster and so on simplify the protection circuit. However, it turns out that even the official USB-blster of Altera cannot avoid such a small probability event. Therefore, Amy electronics guessed that Altera cut down the low-end fpga I/O diode clamp protection circuit to reduce costs.
Recommended plugging Sequence
Cabling Sequence
1. Power off the FPGA Development Board;
2. Connect the JTAG cable of the JTAG simulator to the JTAG interface of the FPGA Development Board;
3. Insert a USB cable to the USB interface of the simulator (assuming another segment of the USB cable has been inserted into the computer );
4. Power on the FPGA Development Board.
Do not switch between steps 2 and 3, because although the FPGA Development Board has no power supply, the USB-powered JTAG simulator will also generate a certain voltage, acting on the VCC And Gnd of the FPGA Development Board, therefore, pay attention to this order.
Disconnection Sequence
1. Power off the FPGA Development Board;
2. Unplug the USB cable from the USB interface of the JTAG simulator;
3. Remove the connection between the JTAG cable and the FPGA Development Board;
Do not switch between steps 2 and 3. The reason is as above.
Summary
Whether it's an FPGA Development Board or another one, the power supply cannot be plugged in with live cables. You must first try to disconnect all connected power supplies before proceeding.
Related
[Note]. For more information, see error: can't access JTAG chain and error: operation failed. It turns out that the JTAG cable is not pressed properly. [JTAG]
[Note]. It hurts !!! Error: can't access JTAG chain, error: operation failed. [JTAG]