Chase H.Q.: Routine at 9E11

9E11: Draws the turbo sprites and updates the displayed scores

Used by the routine at bonus_string.
plot_turbos_and_scores	9E11	LD A,($A170)	If no turbo boosts remain jump to plot_scores_only
	9E14	AND A
	9E15	JR Z,plot_speed_only
	9E17	LD C,A	Preserve number of turbo boosts in C
	9E18	LD A,($A24E)	Read boost time remaining and set flags
	9E1B	AND A	Read boost time remaining and set flags
	9E1C	LD HL,$76F0	Point HL at base of turbo sprites
	9E1F	JR Z,ptas_turbo_setup	Avoid frame increment and address calculation if possible
	9E21	LD A,$00	Get frame number (0, 1 or 2)
	9E23	INC A
	9E24	CP $03
	9E26	JR NZ,plot_turbos_and_scores_0
	9E28	XOR A
plot_turbos_and_scores_0	9E29	LD ($9E22),A	Self modify frame number
	9E2C	JR Z,ptas_turbo_setup	Avoid frame address calculation if possible
	9E2E	LD DE,$0038	56 bytes per frame
	9E31	LD B,A	Calculate the frame address
plot_turbos_and_scores_1	9E32	ADD HL,DE
	9E33	DJNZ plot_turbos_and_scores_1
ptas_turbo_setup	9E35	LD ($9E45),HL	Self modify 9E44 to load SP with address of frame
	9E38	LD ($9E79),SP	Self modify 9E78 to restore SP once drawing is done
	9E3C	LD A,$E1	Low byte of back buffer draw address
Draw a whole frame of turbo sprite. Note that the frame data is stored in memory inverted (bottom first), so we draw the bottom row first and then proceed upwards.
ptas_turbo_loops	9E3E	LD SP,$76F0	Base address of frames
	9E41	DEC C	Temporarily decrement the number of turbos remaining to draw
	9E42	JR NZ,plot_turbos_and_scores_2	All but the final turbo sprite use the zeroth frame
	9E44	LD SP,$0000	SP is pointed at frame data (self modified)
plot_turbos_and_scores_2	9E47	INC C	Restore number of turbos
	9E48	LD H,$FE	Form back buffer position
	9E4A	LD L,A	Form back buffer position
	9E4B	EX AF,AF'	Preserve partial back buffer position
	9E4C	LD B,$0E	Height of frame
Draw a scanline of frame.
ptas_turbo_scanline	9E4E	POP DE	Pop some frame data off the stack (E is mask data, D is bitmap data)
	9E4F	LD A,(HL)	Write to screen: Screen = (Screen AND Mask) OR Bitmap
	9E50	AND E
	9E51	OR D
	9E52	LD (HL),A
	9E53	INC L	Advance screen address to next column
	9E54	POP DE	(Repeat)
	9E55	LD A,(HL)
	9E56	AND E
	9E57	OR D
	9E58	LD (HL),A
	9E59	DEC L	Step back
	9E5A	LD A,H	Move up a row (standard pattern)
	9E5B	DEC H
	9E5C	AND $0F
	9E5E	JP NZ,plot_turbo_continue
	9E61	LD A,H
	9E62	ADD A,$10
	9E64	LD H,A
	9E65	LD A,L
	9E66	SUB $20
	9E68	LD L,A
	9E69	JP NC,plot_turbo_continue
	9E6C	LD A,H
	9E6D	SUB $10
	9E6F	LD H,A
plot_turbo_continue	9E70	DJNZ ptas_turbo_scanline	Loop until out of rows
	9E72	EX AF,AF'	Restore back buffer draw address
	9E73	ADD A,$02	Advance screen address to next turbo position
	9E75	DEC C	Decrement number of turbos
	9E76	JR NZ,ptas_turbo_loops	Loop until none are left
	9E78	LD SP,$0000	Restore SP
plot_speed_only	9E7B	LD DE,$4132	Point DE at speed digits screen position (144, 9)
	9E7E	EXX	Bank
	9E7F	LD DE,($A24A)	Load speed into DE
Scale internal speed (0..511) to displayed speed by multiplying by 82 then discarding the bottom two digits.
	9E83	LD HL,$0000	Initialise counter
	9E86	LD B,$07	Do 7 digits / iterations
	9E88	LD A,$52	Multiplier of 82 (a percentage: speed * multiplier / 100 = displayed speed)
plot_turbos_and_scores_3	9E8A	RLA	Shift one bit out
	9E8B	JR NC,ptas_speed_multiply_loop	Jump if not adding
	9E8D	ADD HL,DE	Add
ptas_speed_multiply_loop	9E8E	ADD HL,HL	Double
	9E8F	DJNZ plot_turbos_and_scores_3	Loop
Count 10,000s.
	9E91	LD BC,$2710	10000
	9E94	LD DE,$FFFF	Initialise D and E counters to -1
	9E97	XOR A	?Clear carry flag?
ptas_speed_10000s_loop	9E98	INC D	Increment counter
	9E99	SBC HL,BC	Decrease total by 10,000
	9E9B	JR NC,ptas_speed_10000s_loop	Loop until HL goes negative
	9E9D	ADD HL,BC	Correct for overshoot
	9E9E	AND A	?Clear carry flag?
Count 1,000s.
	9E9F	LD BC,$03E8	1000
plot_speed_1000s_loop	9EA2	INC E	Increment counter
	9EA3	SBC HL,BC	Decrease total by 1,000
	9EA5	JR NC,plot_speed_1000s_loop	Loop until total goes negative
	9EA7	ADD HL,BC	Correct for overshoot
Count 100s.
	9EA8	XOR A	Initialise counter (to zero not -1 as in previous cases)
	9EA9	LD BC,$0064	100
ptas_speed_100s_loop	9EAC	INC A	Increment counter
	9EAD	SBC HL,BC	Decrease total by 100
	9EAF	JR NC,ptas_speed_100s_loop	Loop until total goes negative
	9EB1	DEC A	Correct for starting early
Plot speed digits. We divide by 100 here by throwing away the bottom two digits.
	9EB2	PUSH AF	Stack 100s counter
	9EB3	LD A,E	Stack 1,000s counter
	9EB4	PUSH AF	Stack 1,000s counter
	9EB5	LD A,D	Get 10,000s counter
	9EB6	CALL ledfont_plot	Plot a digit for 10,000s
	9EB9	POP AF	Plot a digit for 10,000s
	9EBA	CALL ledfont_plot	Plot a digit for 1,000s
	9EBD	POP AF	Plot a digit for 1,000s
	9EBE	CALL ledfont_plot	Plot a digit for 100s
Time.
	9EC1	LD DE,$412F	Point DE at time digits screen position (120, 9)
	9EC4	EXX	Bank
	9EC5	LD DE,$A17E	Point DE at time_bcd (one BCD byte)
	9EC8	LD HL,$A180	Point HL at time_digits + 1
	9ECB	LD B,$01	One pair of digits
	9ECD	CALL ptas_led_digits	Call plot_led_digits
Distance.
	9ED0	LD DE,$A256	Point DE at distance_bcd + 1 (the second of two BCD bytes)
	9ED3	LD A,($A189)	L = Distance byte from first 'hazard' (the perp)
	9ED6	LD L,A	L = Distance byte from first 'hazard' (the perp)
	9ED7	LD A,($A199)	H = 17th byte from first hazard (not sure yet how they relate)
	9EDA	LD H,A
Count 1000s (no loop here - it's not required)
	9EDB	LD BC,$03E8	1,000
	9EDE	SBC HL,BC	Decrease total by 1,000
	9EE0	LD A,$10	BCD "10"
	9EE2	JR NC,plot_turbos_and_scores_4	Jump if distance >= 1,000
	9EE4	ADD HL,BC	Otherwise correct for overshoot
	9EE5	XOR A	BCD "00"
Count 100s
plot_turbos_and_scores_4	9EE6	LD BC,$0064	100
ptas_scores_distance_100s_loop	9EE9	INC A	Increment counter
	9EEA	SBC HL,BC	Decrease total by 100
	9EEC	JP NC,ptas_scores_distance_100s_loop	Loop until total goes negative
	9EEF	ADD HL,BC	Correct for overshoot
	9EF0	DEC A	Correct for starting early
	9EF1	LD (DE),A	distance_bcd[1] = counter
Count 10s
	9EF2	LD C,$0A	10 (B's already zero)
	9EF4	AND A	?Clear carry flag?
	9EF5	LD A,$F0	A = $F0 (BCD)
ptas_scores_distance_10s_loop	9EF7	ADD A,$10	Increment counter
	9EF9	AND A	?Clear carry flag?
	9EFA	SBC HL,BC	Decrease total by 10
	9EFC	JP NC,ptas_scores_distance_10s_loop	Loop until total goes negative
	9EFF	ADD HL,BC	Correct for overshoot
	9F00	OR L	OR in the remainder
	9F01	DEC DE	distance_bcd[0] = A
	9F02	LD (DE),A	distance_bcd[0] = A
	9F03	LD DE,$4191	Point DE at distance digits screen position (136,33)
	9F06	EXX	Bank
	9F07	LD DE,$A256	Point DE at distance_bcd + 1 (two BCD bytes)
	9F0A	LD HL,$A184	Point HL at distance_digits + 3
	9F0D	LD B,$02	Two pairs of digits (4 digits)
	9F0F	CALL ptas_led_digits	Call ptas_led_digits
	9F12	LD DE,$4126	Point DE at score digits screen position
	9F15	EXX	Bank
	9F16	LD DE,$8005	Point DE at score (four BCD bytes)
	9F19	LD HL,$A17C	Point HL at score digits (eight bytes)
	9F1C	LD B,$04	B = 4
Plots scoreboard digits (DE -> BCD) only if different than recorded values (HL -> byte per digit). B is the count.
ptas_led_digits	9F1E	LD A,(DE)	Read a pair of digits (BCD)
	9F1F	LD C,A	Save digits for later
	9F20	RRCA	Unpack a BCD digit
	9F21	RRCA
	9F22	RRCA
	9F23	RRCA
	9F24	AND $0F
	9F26	CP (HL)	If different than stored then plot
	9F27	JR NZ,ptas_led_plot_1st	If different than stored then plot
	9F29	EXX	Move screen position
	9F2A	INC E
	9F2B	EXX
ptas_led_next_half	9F2C	DEC HL	Move to next recorded value
	9F2D	LD A,C	Examine next digit
	9F2E	AND $0F	Examine next digit
	9F30	CP (HL)	If different than stored then plot
	9F31	JR NZ,ptas_led_plot_2nd	If different than stored then plot
	9F33	EXX	Move screen position
	9F34	INC E
	9F35	EXX
ptas_led_next_whole	9F36	DEC HL	Move to next recorded value
	9F37	DEC DE	Move to next digits
	9F38	DJNZ ptas_led_digits	Loop until B is zero
	9F3A	RET	Return
ptas_led_plot_1st	9F3B	LD (HL),A	Update drawn digit
	9F3C	CALL ledfont_plot	Plot the digit
	9F3F	JR ptas_led_next_half	Jump back to handle next digit (second half of a pair)
ptas_led_plot_2nd	9F41	LD (HL),A	Update drawn digit
	9F42	CALL ledfont_plot	Plot the digit
	9F45	JR ptas_led_next_whole	Jump back to handle hext digit (next whole pair)