Routines
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9A55: Noise in/out effect used for mugshots
The counter comes down by one and is stored back. Reaching zero means the effect is over, so print_chatter is called to reveal the face and the message; otherwise the routine falls through and draws the next frame of static.
Used by the routine at drive_chatter.
Input
A Noise effect counter
drive_noise_effect 9A55 DEC A Decrement noise_counter
9A56 LD ($963C),A
9A59 JP Z,print_chatter Exit via print_chatter if it's zero, otherwise fallthrough
This entry point is used by the routine at drive_chatter.
draw_noise_effect 9A5C RRA Shift A's bottom bit into carry
9A5D LD A,$FF A = 255 -- plot_mini_font_cursor_off flag?
9A5F LD D,$20 D = 32 -- ASCII character for plot_mini_font*
9A61 JR C,ne_9a68 If A on input was odd then jump
9A63 CALL plot_mini_font_cursor_on
9A66 JR ne_9a6b else call plot_mini_font_cursor_on and continue at $9a6b
ne_9a68 9A68 CALL plot_mini_font_cursor_off Call plot_mini_font_cursor_off
ne_9a6b 9A6B LD DE,$4036 Set plot address to (176,8)
9A6E LD C,$28 B,C = 4 columns/bytes, 40 rows
ne_9a70 9A70 LD B,$04
9A72 PUSH DE Preserve row ptr
9A73 LD HL,$9634 Point HL at noise_bytes
ne_plot_loop 9A76 LD A,(HL) A = *HL - B -- Subtract row counter (4,3,2,1)
9A77 SUB B
9A78 LD (HL),A *HL++ = A
9A79 INC HL
9A7A RLCA Rotate A left by 1
9A7B ADD A,(HL) *HL += A
9A7C LD (HL),A
9A7D LD (DE),A *DE++ = A -- Store 8 random bits
9A7E INC E
9A7F DJNZ ne_plot_loop Loop while columns remain
9A81 POP DE Restore row ptr
9A82 INC D Move to next row
9A83 LD A,D Usual row movement magic here
9A84 AND $07
9A86 JR NZ,drive_noise_effect_0
9A88 LD A,E
9A89 ADD A,$20
9A8B LD E,A
9A8C JR C,drive_noise_effect_0
9A8E LD A,D
9A8F SUB $08
9A91 LD D,A
drive_noise_effect_0 9A92 DEC C Loop while rows remain
9A93 JP NZ,ne_9a70
9A96 LD A,$47 A = attribute $47 => BRIGHT + white over black
This entry point is used by the routine at drive_chatter.
clear_face_attributes 9A98 LD HL,$5836 Screen attribute position (22,1)
9A9B LD B,$05 5 rows
9A9D LD DE,$001D 32 - 3 = row skip
ne_9a00_loop 9AA0 LD (HL),A Set four attribute bytes
9AA1 INC L
9AA2 LD (HL),A
9AA3 INC L
9AA4 LD (HL),A
9AA5 INC L
9AA6 LD (HL),A
9AA7 ADD HL,DE Move to start of next row
9AA8 DJNZ ne_9a00_loop Loop while rows remain
9AAA RET Return
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