Hi,
I am curious about how the VDP chip accesses video ram. the r/w output on pin 11 (active low) never seems to go low for writing to the VRAM, yet somehow the information gets through.
On my scope, there appears to be spikes instead of square wave, but connected to logic probe there is no change.
Is there anyone with knowledge of Electronics out there who could explain?
PS: I tried adding a logic gate to this pin and the output from that gate is showing up on the probe, but still a spike on the oscilloscope.
Thanks in advance!
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If the screen contents is changing, that is (so run a game, demo or something).
For repairs etc, I find a self-built logic tester a more useful / practical tool (and cheap too!)
I mean, that's some professional piece of hardware, and dozens of hardware builders have been fine building circuits for decades without one. Do you plan to invest the next 5 years of your live in a next-gen MSX model, or what? 