08-15-2011 04:33 AM
I am developing a DVI-controller that transmits a pre-defined pixels data packets (1 red line, 1 green line and 1 blue line, respectively) to an HDMI device.
I am working with SPARTAN 6 FPGA BOARD called ATLYS (Digilent Inc.).
My question is as follows:
1 - I am using a PLL primitive to generate the necessary clocks to drive the DVI encoder module.
I synthesized the project and checked the PLL's clock outputs using the ChipScope.
The primary output of the PLL (CLOKOUT0) was configured to drive a 100MHz clock (identical to the external clock
that I am using in the board).
Unfortunately, I don't see this clock in the ChipScope.
The ChipScope task configuration is as follows:
- TRIGGER LINE : board's master clock - 100MHz
- PLL LOCKED LINE
- PLL CLOKCOUT0 port (100MHz) - non-buffered, connected directly to a BUFPLL primitive (PLLIN port)
- PLL CLOKCOUT1 port (20MHz) - buffered with BUFG
- PLL CLOKCOUT2 port (10MHz) - buffered with BUFG
out of the above configured signals, I see all of them except the CLOCKOUT0 LINE.
Can someone advise me what am I doing wrong here?
08-15-2011 04:37 AM - edited 08-15-2011 05:36 AM
Because the signal you are probing is the same frequency as the trigger, and is (more or less) a constant phase relationship to the trigger, the captured state of the signal will be a constant.
It's very similar to sampling a signal with a register while using the same signal to clock the register. The register output isn't likely to be very interesting.
-- Bob Elkind
08-15-2011 06:09 AM - edited 08-15-2011 06:10 AM
If you want to confirm that the 100MHz CLOCKOUT0 port clock signal is running, and your sampling clock is isochronous and phase-aligned with this 100MHz clock signal -- add a divide-by-2 to your design, and probe this register.
I'm not a chipscope wizard (wish I had a license), this is simply a straightforward workaround suggestion.
-- Bob Elkind
08-15-2011 09:38 AM
In this case, given that I would like to probe the CLOCKOUT0 port signal, how would you suggest me to do that?
Do what we did back in the old days before Chipscope -- bring the signal out to a pin.
08-16-2011 04:24 AM
Was your comment directed at anyone in particular? None of the replies in the thread appear to me to be inflammatory or imply that your question was a homework problem.
I'm a native English speaker from a small, insignificant nation that is often prone to dry, sarcastic wit so I would know if anyone had meant to insult you and can assure you that no offense was intended here.
08-16-2011 08:36 AM - edited 08-16-2011 09:39 AM
Please ignore bassman's "signature" text appended automatically to the end of each of his posts. It is not directed to you.
Bassman is a very generous participant in these forums. He -- and others -- attract direct private messages asking for help on projects or design problems. Often these appeals for help are from students who are not properly prepared for their lab or homework assignment. Bassman's "signature" is directed to these students.
Notice the lengthy list of 'advice' items which appears at the end of my posts. This is my "signature" text, representing a mini-FAQ for new forum readers.
These examples of signature text are not intended for personal insult.
-- Bob Elkind