In SX Microcontrollers, SX/B Compiler and SX-Key Tool, Peter Van der Zee wrote:

Keith, I'm working on a "debug" version of the code I previously posted, so you can see the method I use for tracing out code of THIS nature....others are different.

I'm also adding a much more detailed explanation of how the code works.

Be back to you shortly, going to scope out some more timings; in the meantime I will give some responses to your post.


[quote="Keith M"]

 

I read those times on the datasheet, in the manual, etc too.  I'm not sure why it's taking so long either.  I have a bit set on entry/cleared on exit to the ISR for debugging.  If I measure on my scope from the time the edge falls to the time that bit is set, it's a lot longer.  Now there is some ringing at the bottom of the pulse, but with schmitt triggering, I really should be ok there.  But the pulse isn't square, and so there are multiple (albeit really smaller) falling edges on each pulse.  Maybe I need to put a cap on the input line to help clean this up.

 

No, I don't think a cap is desired. The SX doesn't care about the slope, and using CMOS level should be quite adequate; the edge detection triggers the instant the level drops below half of Vcc, and is in the ISR 3 instruction times (60 uSec) after that.

 

Back in a bit.

 

Peter

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