I decided to start a need thread rather than continue the tangent in this thread: http://forum.allaboutcircuits.com/threads/saving-settings-in-pic-memory.128085/page-2#post-1047873
For those who only read the first few lines, I found this old discussion in the Hi-Tech forum informative: http://forum.htsoft.com/all/showthreaded.php/Cat/0/Number/2138/page/.-/vc/1 Those DS links are still available, if you search in Google by the number.
I decided to see whether I could duplicate the GIE problem with a 12F1840. Here is how the pins were assigned:
MCLR had the usual 10k pull-up and there was decoupling across the power pins. Signal generator was an Asian-branded, dual channel, DDS device. Mode was square wave with 95% duty cycle at various frequencies. Internal oscillator was used at 4 MHz.
My code is attached (GIE Test.zip).
I could not duplicate the GIE problem. Here is one image of the output taken with a 1 kHz stimulus:
Probe_4: LED3 showing normal ISR operation
Probe_3: Stimulus
Probe_2: LED2 showing normal loop (Start --> bra Start) operation
Probe_1: LED1 -- monitors loop created when GIE "problem" exists (theoretical)
Here is a capture with a 2 kHz stimulus and a slower sweep:
I have never observed anything in Probe_1. This morning, I set the 'scope to trigger once on Probe_1 rising edge, and there is nothing after two hours.
Without a positive control, i.e., one of the very early 16Cxx chips (no suffix) or another chip known to show the problem, one can't conclude whether this test would have detected the GIE problem if it existed. Unfortunately, no reputable source currently sells those chips. They are listed on eBay, but those chips don't have a Microchip pedigree. Nevertheless, the evidence -- including the Hi-Tech link and its references -- are consistent with a conclusion that the problem was solved by Microchip last century.
Regards, John
For those who only read the first few lines, I found this old discussion in the Hi-Tech forum informative: http://forum.htsoft.com/all/showthreaded.php/Cat/0/Number/2138/page/.-/vc/1 Those DS links are still available, if you search in Google by the number.
I decided to see whether I could duplicate the GIE problem with a 12F1840. Here is how the pins were assigned:
MCLR had the usual 10k pull-up and there was decoupling across the power pins. Signal generator was an Asian-branded, dual channel, DDS device. Mode was square wave with 95% duty cycle at various frequencies. Internal oscillator was used at 4 MHz.
My code is attached (GIE Test.zip).
I could not duplicate the GIE problem. Here is one image of the output taken with a 1 kHz stimulus:
Probe_4: LED3 showing normal ISR operation
Probe_3: Stimulus
Probe_2: LED2 showing normal loop (Start --> bra Start) operation
Probe_1: LED1 -- monitors loop created when GIE "problem" exists (theoretical)
Here is a capture with a 2 kHz stimulus and a slower sweep:
I have never observed anything in Probe_1. This morning, I set the 'scope to trigger once on Probe_1 rising edge, and there is nothing after two hours.
Without a positive control, i.e., one of the very early 16Cxx chips (no suffix) or another chip known to show the problem, one can't conclude whether this test would have detected the GIE problem if it existed. Unfortunately, no reputable source currently sells those chips. They are listed on eBay, but those chips don't have a Microchip pedigree. Nevertheless, the evidence -- including the Hi-Tech link and its references -- are consistent with a conclusion that the problem was solved by Microchip last century.
Regards, John
Attachments
-
986 bytes Views: 3
Last edited: