A question for YM-2149 experts

All about chiptunes

Moderators: Mug UK, lotek_style, Moderator Team

Post Reply
Tolaemon
Atarian
Atarian
Posts: 7
Joined: Sat Nov 29, 2008 4:27 pm

A question for YM-2149 experts

Post by Tolaemon »

Hi, I have a technical question related to the YM-2149. Hope any of you can help me to solve it.

The problem is that if I update the frecuency of any of it's tone generators successively using it's tone coarse and fine registers ( f.ex R0 and R1 in channel 1 ) sometimes I hear a bit of noise during a short period of time. It seems like the tone oscil.lator desinchronizes while I am updating those registers, and once I've finished it continues playing the right sound.

So for example if I continuously execute this operation to set a frecuency into one of the tone generators:

set ( R0,0xAA) ; //set freq on CH 1 (fine )
set ( R1,0x04) ; // (coarse)

Despite I'am updating all the times the Register with the same frequency, sometimes I hear a desinchronization in the oscillator ( I can see it with an oscilloscope ). What can I do to avoid this ?

I have posted a video to make my question easier to understand http://www.youtube.com/watch?v=ViK7b_1r ... annel_page

Thanks in advance!

Tolaemon

Tolaemon
Atarian
Atarian
Posts: 7
Joined: Sat Nov 29, 2008 4:27 pm

Re: A question for YM-2149 experts

Post by Tolaemon »

Well, I finally found the problem. The cause was that I was not doing the timmings properly. I was not moving the BCDIR and BC1 signal in the exact same way as explained in the datasheet. I checked again the timings and the signals sequence , modified them, and it started to work perfectly. In fact I've discovered that two AY-38912 ( subversion 8338 CDA) which I thought were not working are now working without problems. It is strange to see that the other three AYs ( subversion 8602 CBA ) I have, worked with the old wrong timings but those 8338 did not.

Post Reply

Return to “Ym rockin'”