Gurus for this forum,
I'm a student doing an ASICS and FPGA module at college in the UK and one of my tasks is to build a device using the drag and drop method, no vhdl allowed :( and if im honest, im not that confident using the quartus tools yet, so no doubt this is a newbie question.
The device is a simple alarm clock and to be designed with typical ASM methods, the project was going well until now when im trying to test the control logic.
Im finding that a few of my vector
outputs are showing the hashed pattern symbolising 'forced unknown'. The first instance occurs with a simple SR register in that on setting (1 clock pulse on s) the q will go high one clock later but then one clock after that (1 clock after s goes low again) Q shows the forced unknown pattern, which makes other dependant logic signals forced unknown when their conditions are met for the remainder of the simulation waveform file.
I have tested the SR register independently and a single independent SR Flip-Flop , and it is behaving the same when signalled with the same pulse width via a vectored input pin. ie. appears high for the pulse width (1 clock skew) and then forced unknown there after.
Could this be a design error? or caused by Quartus a setting? can anyone advise?
thanks for your time.
# Luke
