SN76489 polarity
Posted: Wed Apr 29, 2020 8:27 pm
It has been almost 2 decades since I released something to the public. Some might remember me as "Gerrie", author of some old Sega emulators (I lost access to my old mail address, so I created a new account). I recently decided to continue a project which I have been working on and off in the past 20 years or so, as with the worldwide COVID-19 pandemic I have more spare time to spent. More about this project later, if someone is interested.
The past week I have been working on a new SN76489 emulator. I think I have pretty much nailed it, however I do have a couple of questions. As I lost all my documentation and notes, and the fact that I don't have hardware to run tests with I thought it might a good idea to ask here:
Is the SN76489 capable of outputting a negative polarity ?
I've checked various sources but couldn't find a definitive answer; Some emulators do have a negative output, others don't (MAME for example).
I know the output of the noise LFSR is always positive, but I was wondering what the attenuator does when it gets a flip-flop of 0 from the tone channels. (the flip-flop flipping between 0 - 1 when the half tone period reaches 0).
The past week I have been working on a new SN76489 emulator. I think I have pretty much nailed it, however I do have a couple of questions. As I lost all my documentation and notes, and the fact that I don't have hardware to run tests with I thought it might a good idea to ask here:
Is the SN76489 capable of outputting a negative polarity ?
I've checked various sources but couldn't find a definitive answer; Some emulators do have a negative output, others don't (MAME for example).
I know the output of the noise LFSR is always positive, but I was wondering what the attenuator does when it gets a flip-flop of 0 from the tone channels. (the flip-flop flipping between 0 - 1 when the half tone period reaches 0).