Hi,everyone,

I use the 68013's GPIF to read data from an external FIFO. It's strange that when I connect the 68013's data bus to external's output databus,68013 can't renumeration, I disconnect them it can renumeration.

At the beginning I thought the problem  may be at the register GPIFIDLECS which control wether drive the data bus in idle state. So I set the IDLEDRV to be 0, which means not drive the databus in the idle state. But it can't also renumeration.It really confused me. I don't know where the bug is.

I disconnected the databus, then I measure the voltage on the databus pin,they are 3.3 volt.

I ground one of them for a while and them left it not connect. But the voltage on the pin is still 3.3 volt. So I think the databus is outputting. Even though I set it not drive in idle state in register through register GPIFIDLECS.

Hi,

Need a little more information to understand this issue better

When you connect FX2LP to the external FIFO then FX2LP doesn't enumerate? or renumerate (firmware download works but FX2LP doesn't enumerate back)?

I've seen issues like this happen when pins of FX2LP are being driven when the chip is not powered. Are you driving any of the pins of FX2LP when the chip is still not powered?

Regards,

Anand

it can't renumerate,(firmware download works but FX2LP doesn't enumerate back)

yes,  to decrease the control line to external FIFO. The OE pin of external FIFO  is grounded. It means it is driven when the external FIFO be powered. 68013 is powered when it connects to PC. 

I will try this. 

Is it happening with all firmwares i.e. can you download one of our example firmware with the external FIFO connected to see if it renumerates or not? 

I just want to find out if the firmware is stuck somewhere due to the databus being driven.

Regards,

Anand