7555 Clock Issue in Lesson 6 and 7

[ricochet82]

Hi. I bought the CPLD kit and have been working thru the tutorials. It has been a great experience.

I am having problems with the 7555 clock being detected or maybe processed by the CPLD. I have a scope on the clock output and can see it generates consistent clocking, but the output pins are missing counts (e.g. they literally are skipped). For example, in lesson 7 which is currently setup, the LED will cycle thru something like 1,2,3,5,6,7,9 (and this is not consistent).

I discovered if I feed the clock from a function generator, no problem. The only difference I see is the function generator provides 3.6v and the 7555 is providing 3.28v.

I created a separate 7555 running on 5V and fed it's clock to the CPLD. That works 100% correct. I then used a fixed 3.3v power supply that produces about 3.4v and it works nearly correctly on that - dropping only the 0.

You don't have any problem on your videos. I've checked the code and wiring repeatedly and see no problems there.

I'm baffled.

Dan

[ThePyroElectro]

Hi. I bought the CPLD kit and have been working thru the tutorials. It has been a great experience.

I am having problems with the 7555 clock being detected or maybe processed by the CPLD. I have a scope on the clock output and can see it generates consistent clocking, but the output pins are missing counts (e.g. they literally are skipped). For example, in lesson 7 which is currently setup, the LED will cycle thru something like 1,2,3,5,6,7,9 (and this is not consistent).

I discovered if I feed the clock from a function generator, no problem. The only difference I see is the function generator provides 3.6v and the 7555 is providing 3.28v.

I created a separate 7555 running on 5V and fed it's clock to the CPLD. That works 100% correct. I then used a fixed 3.3v power supply that produces about 3.4v and it works nearly correctly on that - dropping only the 0.

You don't have any problem on your videos. I've checked the code and wiring repeatedly and see no problems there.

I'm baffled.

Dan

I know we e-mailed back and forth a few times. I wonder if you ever figured out the issue here.

Seems to be a very, very odd bug.

[ricochet82]

Never did figure it out. Every lesson required 5V on the clock pin to work. I used different CPLDs, 555 timers, power supplies, etc. Completely bizzare. But I've moved on to a MAX II with an onboard clock now.

[ThePyroElectro]

Never did figure it out. Every lesson required 5V on the clock pin to work. I used different CPLDs, 555 timers, power supplies, etc. Completely bizzare. But I've moved on to a MAX II with an onboard clock now.

Sorry I couldn't give you a better answer. I used many different 7555 countless times as a clock both fast and slow and could never reproduce what you saw.

[Ayan Prince]

I wonder if you ever figured out the issue here.



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[ricochet82]

I did not. I moved to an Altera MaxII and never experienced any problems with it.

[ThePyroElectro]

I did not. I moved to an Altera MaxII and never experienced any problems with it.

Glad to hear it worked. Moving to newer technology might have helped as well