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Ok, I guess that asserting two different rows in the dram close enough in time allows charges to be passed from the first row to the second. Looking at the schematics the dram is organized in 32 rows and 8 columns for OAM (plus 1 column for secondary OAM). If the active row(the one OAM points to) is...

Hi, I have been playing around a bit with Visual 2c02 to figure out timing and behavior for OAM-addr and encountered something that seems strange to me. From the information on the wiki: It is also the case that if OAMADDR is not less than eight when rendering starts, the eight bytes starting at OAM...

Yes, that is also what i did, 32 pixel wide bars. That is why the difference is so clear between grays and colors. It was also clear on the scope that it took more than half a period for the different grays to settle.

The lows are supposed to be the same as xD and the highs x0. You might be seeing some low-pass filtering. Yes, both NTSC and PAL nes suffer low pass filtering, that's why the output are triangle waves instead of square. The PAL color burst frequency is also higher (almost 25%) than NTSC so that is ...

Ok, sorry for the late response, but here is all of the data from the measurement. The voltages are measured directly on the video pin on the PPU. Gray scale: 00 : 1270 mV 10 : 1670 mV 20 : 2200 mV 30 : 2200 mV 0d: 448 mV 1d: 640 mV 2d: 1150 mV 3d: 1780 mV Colors: 0x-low: 576 mV 0x-high: 904 mV 1x-l...

I hooked my pal nes up to an oscilloscope today and checked the video-out pin from the ppu, the color burst and regular color waves seem to be equally attenuated so there should be no phaseshift between them. Anyway, what i found interesting was that since the attenuation is pretty high and the wave...

Basically it should be possible to determine the length between the taps on the resistor and determine some relative value, and get some idea what the voltages would be on each tap, then there would also be an additional voltage drop over the pass transistors but i assume that there is not much curr...

There's also a phenomenon called slew rate , where low amplitude signals look more like the third example from the top (exponential rise to high level and fall to low level), whereas high amplitude signals look more like the fourth or even the second (a triangle wave). This happens when certain com...

Ok, so i have been checking the schematics as well, mainly from the link from HardWareMan, and it seems the color-burst output uses its own pass mosfets for the signal voltage levels, as well as synch signal as tepples said. So the resulting voltage on the video out pin is still a mix from three com...

Ok, so you mean that color burst and sync uses the same dac as the video signal, so that would mean that color burst oscillates between super black and one of the other values, or basically output color 0x08? or have i missed something else?

Haha, awesome, so that was you :) So are the first two sets of pictures are from the ppu-output pin? Were the color subcarrier in the video still square then, i couldn't really determine from that thread? Anyways since the color burst seems integrated inside the ppu, unless the color subcarrier is i...

Thanks for the input, i know that a common DAC is wrong in the sense of doing an exact replica, but as long as i can reproduce the correct voltage levels i'm happy, especially since it is a lot simpler to hook up an r-2r DAC than a resistor ladder with pass-mosfets, and i guess it's pretty hard to f...

Hello, i have been doing some development of a VHDL implementation of a NES on an FPGA and have an almost finished PPU and have been doing some experimentation with a composite video interface trying to mimic the original output. I have the interface up and running on my television screen with a har...