Apple-2-SW
/
dos33fsprogs
mirror of https://github.com/deater/dos33fsprogs.git
1
0
Fork 0
Code Issues Projects Releases Wiki Activity

random16: update the cycle counts

This commit is contained in:
Vince Weaver 2018-09-06 01:09:23 -04:00
parent 803591a93c
commit 816d1a81f7
2 changed files with 72 additions and 42 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

57
asm_routines/random16.s
View File

@ -11,35 +11,50 @@ SEEDH = $4F
XOR_MAGIC = $7657 ; "vW"
;=============================
; random16
;=============================
; takes:
; not 0, cc = 5+ = 27
; not 0, cs = 5+12+19 = 36
; $0000 = 5+7+19 = 31
; $8000 = 5+6+14 = 25
; $XX00 = 5+6+7+19 = 37
random16:
lda SEEDL
beq lowZero ; $0000 and $8000 are special values // ; Do a normal shift
asl SEEDL
lda SEEDH
rol
bcc noEor
lda SEEDL ; 3
beq lowZero ; $0000 and $8000 are special values ; 2
asl SEEDL ; Do a normal shift ; 5
lda SEEDH ; 3
rol ; 2
bcc noEor ; 2
doEor:
; high byte is in .A
eor #>XOR_MAGIC
sta SEEDH
lda SEEDL
eor #<XOR_MAGIC
sta SEEDL
rts
; high byte is in A
eor #>XOR_MAGIC ; 2
sta SEEDH ; 3
lda SEEDL ; 3
eor #<XOR_MAGIC ; 2
sta SEEDL ; 3
rts ; 6
lowZero:
lda SEEDH
beq doEor ; High byte is also zero, so apply the EOR
; 1
lda SEEDH ; 3
beq doEor ; High byte is also zero ; 3
; so apply the EOR
; -1
; wasn't zero, check for $8000
asl
beq noEor ; if $00 is left after the shift
asl ; 2
beq noEor ; if $00 is left after the shift ; 2
; then it was $80
bcs doEor ; else, do the EOR based on the carry bit
bcs doEor ; else, do the EOR based on the carry ; 3
noEor:
sta SEEDH
; 1
sta SEEDH ; 3
rts
rts ; 6

57
fireworks/random16.s
View File

@ -11,35 +11,50 @@ SEEDH = $4F
XOR_MAGIC = $7657 ; "vW"
;=============================
; random16
;=============================
; takes:
; not 0, cc = 5+ = 27
; not 0, cs = 5+12+19 = 36
; $0000 = 5+7+19 = 31
; $8000 = 5+6+14 = 25
; $XX00 = 5+6+7+19 = 37
random16:
lda SEEDL
beq lowZero ; $0000 and $8000 are special values // ; Do a normal shift
asl SEEDL
lda SEEDH
rol
bcc noEor
lda SEEDL ; 3
beq lowZero ; $0000 and $8000 are special values ; 2
asl SEEDL ; Do a normal shift ; 5
lda SEEDH ; 3
rol ; 2
bcc noEor ; 2
doEor:
; high byte is in .A
eor #>XOR_MAGIC
sta SEEDH
lda SEEDL
eor #<XOR_MAGIC
sta SEEDL
rts
; high byte is in A
eor #>XOR_MAGIC ; 2
sta SEEDH ; 3
lda SEEDL ; 3
eor #<XOR_MAGIC ; 2
sta SEEDL ; 3
rts ; 6
lowZero:
lda SEEDH
beq doEor ; High byte is also zero, so apply the EOR
; 1
lda SEEDH ; 3
beq doEor ; High byte is also zero ; 3
; so apply the EOR
; -1
; wasn't zero, check for $8000
asl
beq noEor ; if $00 is left after the shift
asl ; 2
beq noEor ; if $00 is left after the shift ; 2
; then it was $80
bcs doEor ; else, do the EOR based on the carry bit
bcs doEor ; else, do the EOR based on the carry ; 3
noEor:
sta SEEDH
; 1
sta SEEDH ; 3
rts
rts ; 6