Routines
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BB0F: convert AY and do (AY)/FAC1
Used by the routines at B9EA, E2B4 and E30E.
Perform divide-by
BB0F 20 8C BA JSR $BA8C unpack memory (AY) into FAC2
This entry point is used by the routine at BB07.
BB12 F0 76 BEQ $BB8A if zero go do /0 error
BB14 20 1B BC JSR $BC1B round FAC1
BB17 A9 00 LDA #$00 clear A
BB19 38 SEC set carry for subtract
BB1A E5 61 SBC $61 subtract FAC1 exponent (2s complement)
BB1C 85 61 STA $61 save FAC1 exponent
BB1E 20 B7 BA JSR $BAB7 test and adjust accumulators
BB21 E6 61 INC $61 increment FAC1 exponent
BB23 F0 BA BEQ $BADF if zero do overflow error
BB25 A2 FC LDX #$FC set index to FAC temp
BB27 A9 01 LDA #$01 set byte
BB29 A4 6A LDY $6A get FAC2 mantissa 1
BB2B C4 62 CPY $62 compare FAC1 mantissa 1
BB2D D0 10 BNE $BB3F branch if <>
BB2F A4 6B LDY $6B get FAC2 mantissa 2
BB31 C4 63 CPY $63 compare FAC1 mantissa 2
BB33 D0 0A BNE $BB3F branch if <>
BB35 A4 6C LDY $6C get FAC2 mantissa 3
BB37 C4 64 CPY $64 compare FAC1 mantissa 3
BB39 D0 04 BNE $BB3F branch if <>
BB3B A4 6D LDY $6D get FAC2 mantissa 4
BB3D C4 65 CPY $65 compare FAC1 mantissa 4
BB3F 08 PHP save FAC2-FAC1 compare status
BB40 2A ROL A shift byte
BB41 90 09 BCC $BB4C skip next if no carry
BB43 E8 INX increment index to FAC temp
BB44 95 29 STA $29,X
BB46 F0 32 BEQ $BB7A
BB48 10 34 BPL $BB7E
BB4A A9 01 LDA #$01
BB4C 28 PLP restore FAC2-FAC1 compare status
BB4D B0 0E BCS $BB5D if FAC2 >= FAC1 then do subtract
FAC2 = FAC2*2
BB4F 06 6D ASL $6D shift FAC2 mantissa 4
BB51 26 6C ROL $6C shift FAC2 mantissa 3
BB53 26 6B ROL $6B shift FAC2 mantissa 2
BB55 26 6A ROL $6A shift FAC2 mantissa 1
BB57 B0 E6 BCS $BB3F loop with no compare
BB59 30 CE BMI $BB29 loop with compare
BB5B 10 E2 BPL $BB3F loop with no compare, branch always
BB5D A8 TAY save FAC2-FAC1 compare status
BB5E A5 6D LDA $6D get FAC2 mantissa 4
BB60 E5 65 SBC $65 subtract FAC1 mantissa 4
BB62 85 6D STA $6D save FAC2 mantissa 4
BB64 A5 6C LDA $6C get FAC2 mantissa 3
BB66 E5 64 SBC $64 subtract FAC1 mantissa 3
BB68 85 6C STA $6C save FAC2 mantissa 3
BB6A A5 6B LDA $6B get FAC2 mantissa 2
BB6C E5 63 SBC $63 subtract FAC1 mantissa 2
BB6E 85 6B STA $6B save FAC2 mantissa 2
BB70 A5 6A LDA $6A get FAC2 mantissa 1
BB72 E5 62 SBC $62 subtract FAC1 mantissa 1
BB74 85 6A STA $6A save FAC2 mantissa 1
BB76 98 TYA restore FAC2-FAC1 compare status
BB77 4C 4F BB JMP $BB4F
BB7A A9 40 LDA #$40
BB7C D0 CE BNE $BB4C branch always
do A<<6, save as FAC1 rounding byte, normalise and return
BB7E 0A ASL A
BB7F 0A ASL A
BB80 0A ASL A
BB81 0A ASL A
BB82 0A ASL A
BB83 0A ASL A
BB84 85 70 STA $70 save FAC1 rounding byte
BB86 28 PLP dump FAC2-FAC1 compare status
BB87 4C 8F BB JMP $BB8F copy temp to FAC1, normalise and return
do "Divide by zero" error
BB8A A2 14 LDX #$14 error $14, divide by zero error
BB8C 4C 37 A4 JMP $A437 do error #X then warm start
This entry point is used by the routine at BA28.
BB8F A5 26 LDA $26 get temp mantissa 1
BB91 85 62 STA $62 save FAC1 mantissa 1
BB93 A5 27 LDA $27 get temp mantissa 2
BB95 85 63 STA $63 save FAC1 mantissa 2
BB97 A5 28 LDA $28 get temp mantissa 3
BB99 85 64 STA $64 save FAC1 mantissa 3
BB9B A5 29 LDA $29 get temp mantissa 4
BB9D 85 65 STA $65 save FAC1 mantissa 4
BB9F 4C D7 B8 JMP $B8D7 normalise FAC1 and return
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