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191 lines
3.4 KiB
ArmAsm
191 lines
3.4 KiB
ArmAsm
; Delays in CPU clocks, milliseconds, etc. All routines are re-entrant
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; (no global data). No routines touch X or Y during execution.
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; Code generated by macros is relocatable; it contains no JMPs to itself.
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zp_byte delay_temp_ ; only written to
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; Delays n clocks, from 2 to 16777215
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; Preserved: A, X, Y, flags
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.macro delay n
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.if (n) < 0 .or (n) = 1 .or (n) > 16777215
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.error "Delay out of range"
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.endif
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delay_ (n)
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.endmacro
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; Delays n milliseconds (1/1000 second)
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; n can range from 0 to 1100.
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; Preserved: A, X, Y, flags
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.macro delay_msec n
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.if (n) < 0 .or (n) > 1100
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.error "time out of range"
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.endif
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delay ((n)*CLOCK_RATE+500)/1000
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.endmacro
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; Delays n microseconds (1/1000000 second).
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; n can range from 0 to 100000.
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; Preserved: A, X, Y, flags
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.macro delay_usec n
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.if (n) < 0 .or (n) > 100000
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.error "time out of range"
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.endif
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delay ((n)*((CLOCK_RATE+50)/100)+5000)/10000
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.endmacro
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.align 64
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; Delays A clocks + overhead
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; Preserved: X, Y
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; Time: A+25 clocks (including JSR)
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: sbc #7 ; carry set by CMP
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delay_a_25_clocks:
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cmp #7
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bcs :- ; do multiples of 7
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lsr a ; bit 0
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bcs :+
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: ; A=clocks/2, either 0,1,2,3
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beq @zero ; 0: 5
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lsr a
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beq :+ ; 1: 7
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bcc :+ ; 2: 9
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@zero: bne :+ ; 3: 11
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: rts ; (thanks to dclxvi for the algorithm)
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; Delays A*256 clocks + overhead
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; Preserved: X, Y
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; Time: A*256+16 clocks (including JSR)
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delay_256a_16_clocks:
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cmp #0
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bne :+
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rts
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delay_256a_11_clocks_:
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: pha
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lda #256-19-22
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jsr delay_a_25_clocks
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pla
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clc
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adc #-1
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bne :-
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rts
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; Delays A*65536 clocks + overhead
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; Preserved: X, Y
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; Time: A*65536+16 clocks (including JSR)
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delay_65536a_16_clocks:
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cmp #0
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bne :+
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rts
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delay_65536a_11_clocks_:
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: pha
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lda #256-19-22-13
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jsr delay_a_25_clocks
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lda #255
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jsr delay_256a_11_clocks_
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pla
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clc
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adc #-1
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bne :-
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rts
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max_short_delay = 41
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; delay_short_ macro jumps into these
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.res (max_short_delay-12)/2,$EA ; NOP
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delay_unrolled_:
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rts
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.macro delay_short_ n
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.if n < 0 .or n = 1 .or n > max_short_delay
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.error "Internal delay error"
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.endif
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.if n = 0
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; nothing
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.elseif n = 2
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nop
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.elseif n = 3
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sta <delay_temp_
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.elseif n = 4
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nop
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nop
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.elseif n = 5
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sta <delay_temp_
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nop
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.elseif n = 6
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nop
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nop
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nop
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.elseif n = 7
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php
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plp
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.elseif n = 8
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nop
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nop
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nop
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nop
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.elseif n = 9
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php
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plp
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nop
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.elseif n = 10
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sta <delay_temp_
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php
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plp
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.elseif n = 11
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php
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plp
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nop
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nop
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.elseif n = 13
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php
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plp
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nop
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nop
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nop
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.elseif n & 1
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sta <delay_temp_
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jsr delay_unrolled_-((n-15)/2)
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.else
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jsr delay_unrolled_-((n-12)/2)
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.endif
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.endmacro
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.macro delay_nosave_ n
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; 65536+17 = maximum delay using delay_256a_11_clocks_
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; 255+27 = maximum delay using delay_a_25_clocks
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; 27 = minimum delay using delay_a_25_clocks
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.if n > 65536+17
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lda #^(n - 15)
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jsr delay_65536a_11_clocks_
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; +2 ensures remaining clocks is never 1
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delay_nosave_ (((n - 15) & $FFFF) + 2)
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.elseif n > 255+27
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lda #>(n - 15)
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jsr delay_256a_11_clocks_
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; +2 ensures remaining clocks is never 1
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delay_nosave_ (<(n - 15) + 2)
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.elseif n >= 27
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lda #<(n - 27)
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jsr delay_a_25_clocks
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.else
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delay_short_ n
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.endif
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.endmacro
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.macro delay_ n
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.if n > max_short_delay
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php
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pha
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delay_nosave_ (n - 14)
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pla
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plp
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.else
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delay_short_ n
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.endif
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.endmacro
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