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PostPosted: Mon Dec 17, 2018 7:22 am 

Joined: Mon Dec 17, 2018 7:20 am
Posts: 1
Hello, I have been working on making a hardware mixer for my nes taking the CPU pin 1, pin 2 and famicom pin 9 and making a line out. one of the features is to separate the signals for effects and creating sync tracks for my other equipment (analogue sync to lsdj). I have gotten pretty close but still have issues with it generating unwanted clicks. I am trying to look for some way to sync the oscillator with the timing of the music my 1 tick blip doesn't capture 2 oscillation instead of one.

i wanted to know if 1 hertz = 1 tick for .nsf (i use famitracker for my chiptunes)? or how i can sync any channels oscillator?

Last edited by ronnysingh on Mon Dec 17, 2018 1:01 pm, edited 1 time in total.

PostPosted: Mon Dec 17, 2018 7:49 am 

Joined: Sun Sep 19, 2004 11:12 pm
Posts: 21394
Location: NE Indiana, USA (NTSC)
NSF specifies PLAY routine call rate as a period value in microseconds. FamiTracker appears to allow specifying play period only as an "engine speed" in integer hertz, and 1000000 μs/s / 60 Hz = 16667 μs. This is slightly slower than 16399 μs that corresponds to the NES PPU's vertical scan rate of 60.1 Hz.

I looked up "famicom pin 9" in expansion port, and pin 9 appears to refer to controller 2's clock signal, which is also available as pin 2 of the NES controller port. There's a known defect in the NTSC Famicom and NES CPU, whose memory controller outputs two clocks in quick succession when controller 1 or 2 is read at exactly the the same time that the DMA unit is retrieving another byte of DPCM data. One workaround is filtering the signal externally; another is performing a sprite DMA immediately before clocking in order to align the odd/even clock phase of the DMA unit. (See also APU DMC conflict glitch.)

Do you get the problem in NSFs that do not use DPCM?

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