If I recall correctly, VRAM writes are not allowed outside v-blank and force-blank. The way the game normally handles VRAM transfers beyond the menu initialization phase is to store the source, destination, and block size in $12-$18 or $19-$1F, and then let the DMA transfer occur on its own whenever an NMI is manually triggered at C3/1368. However, this only lets you update two VRAM blocks at once, so you'd need to set up the DMA transfers for both VRAM fonts, trigger an NMI by calling $1368 to handle this right away, and then set up the transfer for the tilemap update (to refresh the settings on screen), which the game would take care of on the next NMI.
A simple workaround would be to trigger a fade-in whenever the font is changed, which is what Pandora's Box does.
Topic: VRAM updating (FF6 FWF font) **semi-solved** (Read 423 times)