42 lines
821 B
ArmAsm
42 lines
821 B
ArmAsm
// #LAYOUT# STD * #TAKE
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// #LAYOUT# X16 BASIC_0 #TAKE-OFFSET 2000
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// #LAYOUT# * BASIC_0 #TAKE
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// #LAYOUT# * * #IGNORE
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//
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// Math package - multiply FAC1 by 10
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//
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// See also:
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// - [CM64] Computes Mapping the Commodore 64 - page 114
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// - https://www.c64-wiki.com/wiki/Floating_point_arithmetic
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// - https://codebase64.org/doku.php?id=base:kernal_floating_point_mathematics
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//
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mul10_FAC1:
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// Handle special case of FAC1 equal 0
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lda FAC1_exponent
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beq mul10_FAC1_done
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// Start by multiplying FAC1 by 2
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jsr mul10_FAC1_mul2
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// Move FAC1 to FAC2, so that FAC1 = FAC2 = 2 * initial
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jsr mov_FAC1_FAC2
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// Multiply FAC1 by 4
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jsr mul10_FAC1_mul2
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jsr mul10_FAC1_mul2
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// Now we have FAC1 = 8 * initial and FAC2 = 2 * initial; so just add these 2 values
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jmp add_FAC2_FAC1
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mul10_FAC1_done:
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rts
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