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This commit is contained in:
Phil Budne
2016-03-02 18:42:03 -05:00
parent 6547aa98be
commit 08d9d23858
1 changed files with 23 additions and 17 deletions
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40
src/sys/s4.s
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@@ -63,27 +63,33 @@ laci: 0
"** 01-s1.pdf page 22
" skip if AC between two values (inclusive)
" jms betwen; low_ptr; high_ptr
" <not between>
" <between>
" listing has an alternate written in
" (which would require 'lac ptr' instead of 'ptr' args?)
betwen: 0
lmq cmq
lac betwen i
lmq cmq " get ~AC in MQ
lac betwen i " get low_ptr
dac 9f+t
isz betwen
lacq
tad 9f+t i
sma
jmp 1f
lac betwen i
isz betwen " skip low_ptr
lacq " get ~AC (-AC-1) from MQ
tad 9f+t i " get low-AC-1
sma " negative (AC >= low)?
jmp 1f " no, return w/o skip
lac betwen i " fetch high_ptr
dac 9f+t
isz betwen
lacq
tad 9f+t i
cma
spa sna
isz betwen " skip high_ptr
lacq " get -AC-1
tad 9f+t i " add to high value (high-AC-1)
cma " complement (AC-high)
spa sna " AC-high <= 0?
1:
isz betwen
lacq
cma
jmp betwen i
isz betwen " no: give happy return
lacq " restore ~AC
cma " restore AC
jmp betwen i " return w/o skip
copy: 0
-1