Enabling JTAG mode on startup

Spartan-3 USB 2.0 Modules
1

Hi again,

We’re now having some difficulty with JTAG programming, with some strange results! Programming using a bit file through front panel is fine, but when we try to program via JTAG, the system fails to start. iMPACT verifies that the programming was ok, but nothing happens. The really strange part though, is that if we program via front panel first, and then try jtag, it works a treat, even if the jtag config file is different. Unfortunately, after a power-down the only way to configure is through fp again.

We’ve looked into the spartan startup sequence, and think we might have to do something with the INIT or PROG pins, though this doesn’t explain why JTAG works after a USB operation! Any help would, as always, be appreciated.

2

Hello-

It is possible that your device doesn’t have a clock.

If you are using the XEM3001, the current level of firmware does not start the clock when it boots. This process is handled by the software when a bitfile is downloaded via USB.

In response to another customer that wanted to use the XEM3001 in a standalone configuration, we added support to start the PLL upon boot based on the EEPROM PLL settings. This version will be available in our next firmware release. If you need access sooner, please submit a support ticket by emailing [email protected]

Note that the XEM3010 was designed to be used standalone and therefore has this bit of startup code already.