Glitch flash problem

yarisboy

When the attached code has an input transition from 999 rpm to 1000 rpm I'm getting a flash of the last contents of the bank 4 register from before the blanking operation. Is this just a quirk of the MC14489 chip or have I overlooked something. So far delay timers haven't helped. It's usable but annoying.
video:
http://www.youtube.com/watch?v=_jQS9OVaj88

kuroneko

I noticed the characters "0" and "d" during the transition which looks suspiciously like the high nibble of the command you're sending ($01/$D1) when switching between 3/4 digit mode. Can you lower your clock to e.g. 1kHz to make sure it's not a timing issue?

Not much but you never know ...

yarisboy

I'll try that. My clock speed is set by a constant. I changed my configuration byte from $D1, %1101_0001 to $91, %1001_0001. $9 puts bank 4 in special decode so a hex-zero there blanks that digit. $1 in the second nibble leaves banks 1-3 in hex decode and the last bit = 1 puts display intensity high. I may also put a short moving average routine in to cut down on dithering at the transitions. There is enough noise in the one's place to make it meaningless as it stands.