when my signal goes low I am measuring 3.5 microseconds VS the documented 3.7 (fig B), I have all beliefs that this has some good leeway considering when it was "carved in stone" in the late 1980's, but does anyone know how much tolerance 640X480X60hz VGA has in timing?
More Importantly,... Voltage!
When using the timer there is a significant spike when all the transistors in the IC switch, and I have managed to minimize this, to a point.
When goggling "VGA sync voltages" two common answers come up, 0-4.5 volts or "its TTL dude !!!" :
but does anyone know how much tolerance 640X480X60hz VGA has in timing
That is a function of the monitor but most are quite tolerant. There might also be a pot inside the monitor that you could adjust.
As to voltage that should be OK.
If you are just feeding the H-sync it could be that your monitor will not like it until you feed the v-sync in as well. Also most monitors I have seen need h-sync pulses in the v-sync. I do this by feeding the v-sync through an exclusive or gate with the other input coming from the h-sync. It is not quite spec but usually works.
OK never heard it called that but yes the method of delivery of the sync pulse doesn't matter. In this case it is a 0.3v to 0V transition with the green digital signal above it, a bit like a standard composite video signal.
Well I have 1 556 timer generating a clean h-sync signal, and on the other side of that timer the h porch signals.
I gather the porch signals are not really mission critical, especially on nice new modern monitors, but whats your experience with it ?
Going to start working on the vertical signals today, which ought to go fast as its more or less a dupe of the first 556 circuit
Then I get to go grab the el-crappyo 15 inch gateway crt monitor thats been sitting in my trunk for 2 years now, cause if somethings going to get messed up on the first try, id rather it not be my el-crappyo LCD, since the crt wont fit on my desk lol