Chase H.Q.: Routine at F7AA

F7AA: Sets up the classic ZX Spectrum IM2 "257-byte table" interrupt vector trick

Fills $BC00-$BDBD with the byte $BD so that, whatever the low byte of the interrupt vector happens to be, the CPU always resolves it to the single byte at $BDBD; patches that byte to a JP opcode ($C3) whose operand ($BDBE/$BDBF) is set to frame_interrupt_handler, making $F8AD the interrupt handler for every subsequent interrupt. Sets I to the table's page and enables IM 2. Used by the routines at insert_high_score_entry, run_title_screen, play_success_music and options_menu_driver.
setup_im2_interrupt_table	F7AA	LD HL,$BC00
	F7AD	LD A,H
	F7AE	LD B,$00
	F7B0	LD C,$BD
setup_im2_interrupt_table_0	F7B2	LD (HL),C
	F7B3	INC HL
	F7B4	DJNZ setup_im2_interrupt_table_0
	F7B6	LD (HL),C
	F7B7	LD I,A
	F7B9	IM 2
	F7BB	LD A,$C3
	F7BD	LD ($BDBD),A
	F7C0	LD HL,$F8AD
	F7C3	LD ($BDBE),HL
	F7C6	RET