Forums

LPC2000 and Xilinx CPLD in one JTAG chain

Started by kender_a August 28, 2009
Colleagues,

Is it possible to have an LPC2368 and a Xilinx CPLD (running on +3.3V) on the same JTAG chain? Should LPC always be the 1st device in the chain? Are there caveats? Are there app notes describing something like that?

The JTAG connector pinouts are different for LPC2000 and Xilinx. I'm planning to have an LPC pinout on the board and a separate adapter for Xilinx.

Any suggestion or insight is appreciated!

- Nick

An Engineer's Guide to the LPC2100 Series

Hi,

IMHO, I think it will work. The JTAG basically is just sending data and clock (quite similar to SPI), but interpreting the data is another story.

Most probably the Xilinx's JTAG wont be able to recognize the ARM debug data and vice versa. You will need to set the debugger to skip the device.

One of clear example, if I'm not mistaken, is the Phytec-LPC3250 main board. If you plug the J-Link or U-link from Keil, you will see 2-devices: LPC3250 and unknown device. I bet that's the CPLD on the board to control the LCD signals.

Anyway, I haven't touch Pythec-LPC3250 for a while, so I may be mistaken. You'd better check yourself.

Regards,
-daniel
--- On Fri, 8/28/09, kender_a wrote:

> From: kender_a
> Subject: [lpc2000] LPC2000 and Xilinx CPLD in one JTAG chain
> To: l...
> Date: Friday, August 28, 2009, 7:29 PM
> Colleagues,
>
> Is it possible to have an LPC2368 and a Xilinx CPLD
> (running on +3.3V) on the same JTAG chain? Should LPC
> always be the 1st device in the chain? Are there
> caveats? Are there app notes describing something like
> that?
>
> The JTAG connector pinouts are different for LPC2000 and
> Xilinx. I'm planning to have an LPC pinout on the
> board and a separate adapter for Xilinx.
>
> Any suggestion or insight is appreciated!
>
> - Nick