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.
Relevant datasheets:
*[[Media:YMF288.pdf|OPN3 (ymf288) datasheet (Japanese)]]
*[[Media:YM2608J Translated.pdf|YM2608 datasheet (English)]]
The OPN3 chip is a light version of the YM2608 with some functionalities removed.
= Links =