Extreme JTAG programmers

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spman

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Hi

According to this fact that the JTAG is a standard protocol, why does each vendor have its own USB-JTAG device? If we have a USB to JTAG converter, why don't we use it for every JTAG compatible device?

Why must we pay a lot for every USB-JTAG programmer!? So foolish Platform Cable USB, Altera Blaster, ARM JLink ...

Thanks in advance
 

spman said:
According to this fact that the JTAG is a standard protocol, why does each vendor have its own USB-JTAG device? If we have a USB to JTAG converter, why don't we use it for every JTAG compatible device?
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In theory it is certainly possible, there are several "Universal JTAG programmer/debuggers available.

For example:




However, the issue is not just the allowable differences in the hardware interface, device timing, etc.

A major hurdle is writing the vast number of unique drivers/device description files required to successfully communicate with the multitude of devices which offer a JTAG interface.

Keeping up with changes in device revisions alone is a daunting task.

Which is why JTAG programmer/debuggers like the BDI3000 are typically in the $2500 to $30,000 range depending on the number of supported device families and compiler toolchains.


BigDog
 
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    spman

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I wasn't satisfied. I think the interface and description of various devices is not important as there is a standard protocol. Why different drivers? The communication is performed via the JTAG standard. doesn't it?
 

Yes the communication protocol is the same TAP controller FSM but the bsdl files for each device are different and the device's specific USER defined codes are different and must be accounted for in the software driver that would reside on the host system. So as bigdogguru mentions those JTAG programmers that support multiple vendors/parts are in the $2500-$30,000 range. Most of that cost isn't the hardware programmer (perhaps less than $100) it's the team of software engineers that you're paying for that wrote all the drivers for all those vendors/parts.
 

As far as I know, there is no standard for the interface a JTAG programmer presents to the PC.
They may all use (say) USB or serial, but the protocol on top of that has no standard. Nor is there any
standard API (so that the PC application software could work with different drivers, even if the
protocol was different per programmer..). It is a real shame for us, but convenient for the JTAG
programmer and software manufacturers.
 

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