After a post on Facebook by the moderator of the Z80 DIY group I decided to make the schematics and simulate the VGA sync/blanking generator that I've been thinking of for a while.
The ultimate goal is to make this circuit into a 80x25 character "video card" that uses only plain TTLs, a Character ROM and some RAM.
So far I''m using three counter ICs and 6 logic gates ICs for a total of 9 ICs, but I also use 3 diodes and a pulldown resistor as a discrete NOR (cheating a bit)
Simulations in Logisim is ok, and an actual build on a solderless breadboard measures as expected on my oscilloscope.
Next step is to hook it up do a monitor and XOR one bit each of the Ver- & Hor-counters together to get a nice checkerboard pattern on the monitor.