USB and JTAG are two different protocols used for different purposes. USB, or Universal Serial Bus, is a common interface used for connecting various devices to a computer, such as printers, keyboards, and external storage devices. It provides a way for devices to communicate with the computer and transfer data.
On the other hand, JTAG, or Joint Test Action Group, is a standard for testing and debugging integrated circuits, such as microprocessors and programmable logic devices. It allows for the communication and control of individual pins on a device, which can be used for tasks such as programming, debugging, and boundary scan testing.
So, in short, USB and JTAG are not the same thing. However, it is possible to use a USB interface to connect to a JTAG scan chain or to access an SPI (Serial Peripheral Interface) interface on a board. This is where the JTAG-USB cable comes into play.
The JTAG-USB cable is specifically designed to bridge the gap between USB and JTAG. It provides a physical connection between the USB port on your computer and the JTAG or SPI interface on a board. This allows you to use your PC to program devices on Digilent programmable logic boards using the Digilent Adept Suite software.
I have personally used the JTAG-USB cable for programming and debugging FPGA (Field-Programmable Gate Array) devices on Digilent boards. It provides a convenient way to connect to the JTAG interface on the board and perform tasks such as configuring the FPGA or downloading bitstream files.
One important thing to note is that not all devices or boards support JTAG or have a JTAG interface. It is specific to certain types of devices and is not a universal feature. So, if you are planning to use a JTAG-USB cable, make sure that your board or device supports JTAG and has the necessary 6-pin header for connecting the cable.
In addition to JTAG, the JTAG-USB cable can also be used to access the SPI interface on a board. SPI is a serial communication protocol commonly used for interfacing with devices such as flash memory, sensors, and other peripherals. By connecting the JTAG-USB cable to the SPI interface on a board, you can use software tools to communicate with and control SPI devices.
To sum up, USB and JTAG are not the same thing, but the JTAG-USB cable allows you to connect a USB interface to a JTAG or SPI interface on a board. This enables you to program devices and access peripheral interfaces using your computer.