03DF: 3E 40         ld   a,$40          ; CTC base interrupt vector = 0x40
03E1: D3 20         out  ($20),a
03E3: 3E 47         ld   a,$47          ; CTC set int off, counter (/16, auto), falling, TC, res, ctrl
03E5: D3 21         out  ($21),a        ; apply to CTC channel 1
03E7: D3 22         out  ($22),a        ; apply to CTC channel 2
03E9: 3E 50         ld   a,$50          ; set CTC channel 1 time constant to 0x50 (80)
03EB: D3 21         out  ($21),a
03ED: 3E 05         ld   a,$05          ; set CTC channel 2 time constant to 0x05 (5)
03EF: D3 22         out  ($22),a
03F1: D3 C6         out  ($C6),a        ; ?????? what voodoo is this unknown I/O port
03F3: 3E A7         ld   a,$A7          ; CTC channel 3 int on, timer mode, /256, falling, auto, TC, res, ctrl
03F5: D3 23         out  ($23),a
03F7: 3E 9C         ld   a,$9C          ; set CTC channel 3 time constant to 0x9c (156)
03F9: D3 23         out  ($23),a