You can use the &F888/&F988 audio ports and the CRTC cursor registers to program the raster interruption located at &0066. Both works on PlayCity and Play2CPC.
The OPN3 soundchip is mostly a light version of the OPNA soundchip with some functionalities removed: no external ADPCM, no CSM Composite Sine Mode and no GPIO.
Relevant datasheets: [[Media:YMF288.pdf|OPN3 (ymf288) (Japanese)]] and [[Media:YM2608J Translated.pdf|OPNA (ym2608) (English)]]