otomatalabs/furnace
7
0
Fork 0
Code Issues Pull requests Actions Packages Projects Releases Wiki Activity

Update sms.md

Browse source
This commit is contained in:
freq-mod 2024-11-22 13:46:34 +01:00 committed by GitHub
parent f843039e04
commit 4fffb76071
No known key found for this signature in database
GPG key ID: B5690EEEBB952194
1 changed files with 1 additions and 1 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

2
doc/7-systems/sms.md
View file

@ -4,7 +4,7 @@ a relatively simple sound chip made by Texas Instruments. a derivative of it is
nominal mode of SN76489 has 3 square wave channels, with noise channel having only 3 preset frequencies to use (absurdly low, very low, low). to use more pitches, one can enable a mode which "steals" the frequency from square wave channel 3. by doing that, SN76489 becomes effectively a 3 channel sound chip. in addition, periodic noise mode can be enabled, with same caveats.
the original iteration of the SN76489 used in the TI-99/4A computer, the SN94624, could only produce tones as low as 100Hz, and was clocked at 447 KHz. all later versions (such as the one in the Master System and Genesis) had a clock divider but ran on a faster clock... except for the SN76494, which can play notes as low as 13670 Hz (A -1). as a result, its pitch accuracy for higher notes is compromised.
the original iteration of the SN76489 used in the TI-99/4A computer, the SN94624, could only produce tones as low as 100Hz, and was clocked at 447 KHz. all later versions (such as the one in the Master System and Genesis) had a clock divider but ran on a faster clock, making a chip **very** high pitched... except for the SN76494, which can play notes as low as 13.670 Hz (A -1). as a result, its pitch accuracy for higher notes is compromised.
## SN7 versions