Re: JTAG question

Hi

Thanks for the info

I assume that through the JTAG some external flash can also be programmed
that has been wired to an ARM device.


"PeteS" <ps@xxxxxxxxxxxxxxxxxxx> wrote in message
news:1135846324.935227.190570@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> Sagaert Johan wrote:
> > I have a jtag programmer for xilinx devices ,is this a standard
interface ?
> > Can i use this device to program other devices with a JTAG interface (eg
> > ARM ) ?
> > Or do i need a dedicated tjag interface for every Jtag device i intend
to
> > use ? (whats the use of a JTAG standard then ?)
> >
> > Johan
>
> The standard JTAG interface is for test (JTAG stands for 'Joint Test
> Action Group'). The IEEE 1149.1 standard is for that. The 1532 standard
> [IEEE Standard for Boundary-Scan-based In System Configuration of
> Programmable Devices (IEEE 1532)] at
> http://grouper.ieee.org/groups/1532/ specifies using the JTAG interface
> in a standard way for such things as ISP FPGAs.
>
> The method used by various cores may or may not actually program that
> device - often it loads RAM or programs attached flash. There are
> 'standards' for these interfaces in terms of protocol (ARM uses a
> particular [wiggler] interface for this and debug functionality, MIPS
> uses EJTAG, for instance).
>
> At the physical layer, these devices are all roughly the same for the
> JTAG portion (with the notable exception of TRST on Xilinx and a
> number of other mfr's devices) but those other functions (accessing
> internal debug registers for runtime ICE, for instance) requires other
> pins. ARM requires the reset signal to be operated by the JTAG
> debugger, as yet another example.
>
> Note that the JTAG standard is a standard. It's all the things built on
> top of it that aren't.
>
> Cheers
>
> PeteS
>


.

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