For the thread's general reference, a current datasheet link :
https://manufacture1.alldatasheet.com/datashe … AD1821JS-M.html
"The AD1821 MODIO(tm) (Modem over Audio) SoundComm(R) HSP (Host Signal Processing) Codec is a single chip audio and communications subsystem for personal computers. The AD1821 solution includes the AD1821 mixed-signal controller IC and MODIO(tm) host signal processing software drivers. The AD1821 maintains full legacy compatibility with applications written for SoundBlaster Pro and AdLib, while servicing Microsoft PC 97 application requirements. The AD1821 includes an internal OPL3 compatible music synthesizer, ......"
Supporter of PicoGUS, PicoMEM, mt32-pi, WavetablePi, Throttle Blaster, Voltage Blaster, GBS-Control, GP2040-CE, RetroNAS.