Xilinx lets you reuse their jtag hardware after the bit image is loaded. You
instantiate a jtag component , connect your registers to it and add
it into the bsdl file.

John Eaton



On Sun, Jan 8, 2012 at 8:06 AM, Franck JULLIEN <[email protected]>wrote:

> Hi,
>
> After make my CPU work under Modelsim, I started to take a look at the
> JTAG / debug interface when I realized I needed two JTAG on my board.
>
> As I'm using an Altera eval board (DE1 and NEEK), I have an integrated
> JTAG interface (hardware built-in into the board).
> So I need to use my USB-Blaster plugged on GPIOs using a special cable
> in order to get OpenOCD running.
> Doesn't sound's good and I don't like it.
>
> I'm thinking of doing some UART to WISHBONE bus IP. This IP would have
> some GPIO (to control cpu reset for example) and a mechanism switching
> between the standard UART and the controlling software. The
> controlling software would be able to download files to RAM (or SPI
> FLASH, CFI,....), read/write/modify some addresses.
>
> This kind of interface would be slow but I think I worth it. It could
> be an easy way to run test program.
>
> I know there is already a comparable IP on Opencores. However, it is
> not wishbone compliant and I don't like to reuses someone else's code
> when it's not as a blackbox.
> Moreover, there is no controlling software.
>
> What do you think about this ?
>
> Franck.
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>
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