completelyuseless
Junior Member level 1
Hello Everyone,
I have an interesting problem, Its for a small PLD so only logic no core macros, etc.
I have a system clock, an oscillator, I need to check its validity. to generate something very much like a "locked" signal out of a DCM or MMCM block.
Here is the catch. I DONT have a reference clock or any secondary clock.
I am of the opinion that using a clock to check its own status is somewhat self defeating and I don't know if that's even very wise either.
The only alternative I can think of is to update a counter in a register and read that register from an SPI link that I do happen to have. (don't get excited, the SPI clock IS NOT always present and cannot be used as the reference clock) This isn't ideal as there needs to be a spi register interaction to determine if the clock is valid. To invalidate the clock would therefore entail reading a non updated register value in that register for a given period. Not ideal at all because I need that clock "valid signal" for combinatorial logic elsewhere.
Is there a smart way (if at all possible) to do check a clocks validity with itself only and no reference and also be DO-254 compliant?
many thanks in advance
the village idiot :-?
I have an interesting problem, Its for a small PLD so only logic no core macros, etc.
I have a system clock, an oscillator, I need to check its validity. to generate something very much like a "locked" signal out of a DCM or MMCM block.
Here is the catch. I DONT have a reference clock or any secondary clock.
I am of the opinion that using a clock to check its own status is somewhat self defeating and I don't know if that's even very wise either.
The only alternative I can think of is to update a counter in a register and read that register from an SPI link that I do happen to have. (don't get excited, the SPI clock IS NOT always present and cannot be used as the reference clock) This isn't ideal as there needs to be a spi register interaction to determine if the clock is valid. To invalidate the clock would therefore entail reading a non updated register value in that register for a given period. Not ideal at all because I need that clock "valid signal" for combinatorial logic elsewhere.
Is there a smart way (if at all possible) to do check a clocks validity with itself only and no reference and also be DO-254 compliant?
many thanks in advance
the village idiot :-?