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What is JTAG and how can I make use of it?
You may be familiar with JTAG because you have used tools with a JTAG interface. Processors often use JTAG to provide access to their debug/emulation functions and all FPGAs and CPLDs use JTAG to provide access to their programming functions. JTAG is not JUST a technology for processor debug/emulation.
What are the characteristics of a JTAG interface?
Electrical characteristics. A JTAG interface is a special interface added to a chip. Depending on the version of JTAG, two, four, or five pins are added. The four and five pin interfaces are designed so that multiple chips on a board can have their JTAG lines daisy-chained together if specific conditions are met.
Why do you need a JTAG connection test?
A JTAG connection test will check that the connections around the JTAG enabled devices on a board are the same as those specified in the design. Where two JTAG enabled pins are meant to be connected the test will make sure one pin can be controlled by the other.
What’s the name of the protocol in JTAG?
The name of a protocol: The JTAG specification doesnt even define the protocol for how data is passed between debugger and debugee (i.e. there is no .h file you can reference defining a “JTAG packet” to be passed over a serial, parallel, or USB cable to a target)
Why do FPGAs and CPLDs use JTAG technology?
Processors often use JTAG to provide access to their debug/emulation functions and all FPGAs and CPLDs use JTAG to provide access to their programming functions. JTAG is not JUST a technology for processor debug/emulation.
How does JTAG / boundary scan reduce development costs?
JTAG / boundary scan significantly reduces such development costs because it provides a simplified interface to control the IO pins used to interact with peripherals. This standard interface, which is the same for all JTAG enabled devices, means a generic set of test models can be used, and re-used, when building test systems.
By providing a mechanism to control and monitor all the enabled signals on a device from a four-pin TAP, JTAG significantly reduces the physical access required to test a board. There are two main ways that this boundary scan capability can be used to test a board.
What is easier Rgh or JTAG?
Overall, RGH is a more convenient method, but the JTAG boot times are more stable where as RGH can take 5 minutes one boot then 2 secods the next. JTAGable Xbox’s are also much more difficult to find these days, were as RGH is considerably easier to find.