ijor wrote:If you can scope the 1040, yes, that would be nice. Not only because I expect a possible different delay between both signals, but also because the IMP part should have a different clock circuit inside, even the pinout is slightly different.
I'll do that tomorrow. My non-IMP ST still has all the original EMC metal shielding in place, so it takes some time to disassemble it.
If you check the schematics, you can see the non-IMP part has a xtal feed back on pin 1 (normally connected with a pull down). The IMP part has no feed back, and pin 1 is used for the BLANK signal coming from GLUE.
Interesting, I didn't know that! However, this is not the case for my 1040STfm with full IMP chipset. Pin 1 of the shifter still is connected to ground via a 10k resistor. Do you know why the IMP shifter has a BLANK signal input when it still works when this pin is this is permanently pulled to ground as in my machine?
That's exactly my point, they are quite different. See czietz capture at the highest timebase (5ns). The 32 MHZ signal rise and fall time are almost twice the time than the 16 MHZ ones. Also the shape of the wave is quite different. The 16 MHZ is pretty much a square wave, but the 32 MHZ is much more sinusoidal.
The 16 MHz signal originates from the output stage of the shifter, while the 32 MHz signal comes from a discrete amplifier. I suppose the IC's output stage is simply faster than the two transistor amplifier.