Post by Anthony OrtizOkay, so I'm using an SN74LVC245A Octal Bus Transceiver to
level-translate and buffer my Apple IIgs 1mhz (Phase 0) timer signal from
5v down to 3.3v and I am seeing some noise (or whatever it is) when
reading the signal. Here is a pic of the source clock (top) and the
https://drive.google.com/file/d/0B-ZQ2AnS2r_6RlNrTW1tTDhvODhEZTdwUExXS2hDSEQ0aU1Z/view?usp=sharing
I see over/under shoot, don't know if that's normal, but the high-level
of the 3.3v signal has less overshoot but more wavy than the low level;
definitely not symmetrical! When polling the translated 3.3 clock signal
on my Pi in a tight loop I get the data seen at the end of this post.
Any ideas?
[0 is LO, 1 is HI] followed by number of sequential occurrences
0 = 14076,1 = 34867,0 = 1,1 = 11,0 = 1,1 = 3,0 = 3,1 = 2,0 = 1,1 = 3,0 =
1,1 = 2,0 = 2,1 = 2,0 = 6,1 = 2,0 = 6,1 = 2,0 = 2,1 = 3,0 = 5,1 = 2,0 =
2,1 = 2,0 = 2,1 = 1,0 = 1,1 = 1,0 = 5,1 = 1,0 = 9,1 = 1,0 = 31670,1 =
34797,0 = 1,1 = 11,0 = 1,1 = 42,0 = 1,1 = 3,0 = 3,1 = 2,0 = 1,1 = 3,0 =
1,1 = 2,0 = 3,1 = 1,0 = 7,1 = 1,0 = 3,1 = 2,0 = 29631,1 = 34870,0 = 1,1 =
11,0 = 1,1 = 11,0 = 2,1 = 2,0 = 2,1 = 29,0 = 1,1 = 3,0 = 1,1 = 7,0 = 1,1
= 3,0 = 2,1 = 3,0 = 1,1 = 1,0 = 3,1 = 1,0 = 31725,1 = 34871,0 = 1,1 = 3,0
= 1,1 = 7,0 = 1,1 = 3,0 = 1,1 = 2,0 = 1,1 = 3,0 = 1,1 = 1,0 = 1,1 = 1,0 =
1,1 = 11,0 = 1,1 = 4,0 = 1,1 = 3,0 = 1,1 = 2,0 = 2,1 = 3,0 = 1,1 = 1,0 =
3,1 = 2,0 = 31674,1 = 32819,0 = 1,1 = 55,0 = 1,1 = 2,0 = 1,1 = 3,0 = 3,1
= 2,0 = 1,1 = 1,0 = 3,1 = 2,0 = 1,1 = 1,0 = 1,1 = 1,0 = 1,1 = 2,0 = 3,1 =
1,0 = 3,1 = 2,0 = 5,1 = 1,0 = 31686,1 = 34733,0 = 1,1 = 49,0 = 1,1 = 8,0
= 1,1 = 2,0 = 1,1 = 1,0 = 3,1 = 2,0 = 3,1 = 1,0 = 8,1 = 1,0 = 31688,1 =
34876,0 = 1,1 = 1,0 = 1,1 = 9,0 = 1,1 = 3,0 = 1,1 = 4,0 = 1,1 = 3,0 = 1,1
= 2,0 = 2,1 = 2,0 = 1,1 = 4,0 = 1,1 = 7,0 = 1,1 = 3,0 = 1,1 = 2,0 = 1,1 =
4,0 = 1,1 = 2,0 = 1,1 = 2,0 = 1,1 = 1,0 = 1,1 = 2,0 = 1,1 = 1,0 = 1,1 =
1,0 = 1,1 = 1,0 = 3,1 = 1,0 = 31692,1 = 32839,0 = 1,1 = 52,0 = 3,1 = 2,0
= 7,1 = 1,0 = 31691,1 = 34818,0 = 1,1 = 11,0 = 1,1 = 42,0 = 3,1 = 1,0 =
8,1 = 1,0 = 1,1 = 1,0 = 1,1 = 1,0 = 1,1 = 1,0 = 31720,1 = 32839,0 = 1,1 =
40,0 = 1,1 = 2,0 = 2,1 = 1,0 = 3,1 = 2,0 = 31699,1 = 34860,0 = 1,1 = 18,0
= 1,1 = 7,0 = 2,1 = 2,0 = 2,1 = 2,0 = 2,1 = 2,0 = 4,1 = 3,0 = 3,1 = 2,0 =
3,1 = 1,0 = 1,1 = 2,0 = 20,1 = 1,0 = 1,1 = 1,0 = 31670,1 = 34767,0 = 1,1
= 3,0 = 1,1 = 2,0 = 2,1 = 5,0 = 2,1 = 2,0 = 7,1 = 2,0 = 1,1 = 2,0 = 1,1 =
3,0 = 2,1 = 3,0 = 1,1 = 3,0 = 1,1 = 2,0 = 2,1 = 2,0 = 2,1 = 1,0 = 3,1 =
1,0 = 4,1 = 1,0 = 31673,1 = 32906,0 = 1,1 = 6,0 = 2,1 = 6,0 = 2,1 = 2,0 =
33,1 = 1,0 = 31608,1 = 34914,0 = 1,1 = 12,0 = 1,1 = 6,0 = 2,1 = 2,0 = 6,1
= 1,0 = 26,1 = 1,0 = 17,1 = 1,0 = 31721,1 = 32810,0 = 2,1 = 3,0 = 1,1 =
1,0 = 3,1 = 5,0 = 3,1 = 1,0 = 7,1 = 2,0 = 1,1 = 1,0 = 3,1 = 2,0 = 3,1 =
1,0 = 2,1 = 1,0 = 1,1 = 1,0 = 1,1 = 2,0 = 2,1 = 2,0 = 2,1 = 6,0 = 31696,1
= 34814,0 = 1,1 = 2,0 = 1,1 = 3,0 = 1,1 = 3,0 = 2,1 = 5,0 = 3,1 = 1,0 =
3,1 = 2,0 = 1,1 = 6,0 = 2,1 = 2,0 = 3,1 = 2,0 = 1,1 = 3,0 = 1,1 = 2,0 =
3,1 = 1,0 = 2,1 = 1,0 = 31632,1 = 34870,0 = 1,1 = 3,0 = 1,1 = 51,0 = 2,1
= 1,0 = 3,1 = 1,0 = 2,1 = 3,0 = 1,1 = 1,0 = 29726,1 = 34810,0 = 3,1 = 1,0
= 1,1 = 1,0 = 1,1 = 1,0 = 2,1 = 3,0 = 1,1 = 2,0 = 2,1 = 2,0 = 3,1 = 1,0 =
3,1 = 2,0 = 11,1 = 1,0 = 1,1 = 1,0 = 3,1 = 1,0 = 9,1 = 1,0 = 3,1 = 1,0 =
1,1 = 1,0 = 31615,1 = 34848,0 = 1,1 = 27,0 = 1,1 = 7,0 = 2,1 = 5,0 = 1,1
= 3,0 = 3,1 = 6,0 = 1,1 = 2,0 = 2,1 = 2,0 = 31747,1 = 32873,0 = 1,1 = 7,0
= 1,1 = 3,0 = 2,1 = 1,0 = 3,1 = 2,0 = 21,1 = 1
Looks like a lot of ringing.
Are you using a 10x probe? A 1x probe will produce this effect. Using a
effect of the probe and its cable.
circuit.