Hi Ganesh! It depends what registers he was talking about. I think he meant the processor core registers (r1, r2, r3, etc.). You can't control that via JTAG since jtag can just control the boundary scan cells which in turn can only control the chip's pins.
> Ofcourse, you can read the processor register and do many more stuff via
> JTAG. That is provided you know the private JTAG instruction of the
> processor on Assabet (ARM ?). This private instruction set is usually not
> disclosed by the processor vendor in their Boundary scan description
> language (BSDL) file.
>
> > After reading the JTAG code for Assabet I understand that once
> > the boundary scan interface is entered via extest function the whole board
> > as
> > a whole becomes a slave of the JTAG controller. That is the core loses its
> > functionality and becomes dummy and the JTAG controller has the entire
> > rights
> > for all the pins. Now I would like to know that whether it is possible to
> > control the core operations via JTAG? That is is it possible to read any
> > processor registers?
--
Regards
Abraham
we:
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