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-rw-r--r--amforth-6.5/avr8/words/cas.asm28
1 files changed, 28 insertions, 0 deletions
diff --git a/amforth-6.5/avr8/words/cas.asm b/amforth-6.5/avr8/words/cas.asm
new file mode 100644
index 0000000..f59ae26
--- /dev/null
+++ b/amforth-6.5/avr8/words/cas.asm
@@ -0,0 +1,28 @@
+; ( new old addr -- f )
+; Multitasking
+; Atomic Compare and Swap: store new at addr and set f to true if contents of addr is equal to old.
+VE_CAS:
+ .dw $ff03
+ .db "cas",0
+ .dw VE_HEAD
+ .set VE_HEAD = VE_CAS
+XT_CAS:
+ .dw PFA_CAS
+PFA_CAS:
+ movw zl, tosl
+ loadtos
+ ldd temp0, Z+0
+ ldd temp1, Z+1
+ cp tosl, temp0
+ cpc tosh, temp1
+ loadtos
+ brne PFA_CAS1
+ std Z+0, tosl
+ std Z+1, tosh
+ ser tosl
+ rjmp PFA_CAS2
+PFA_CAS1:
+ clr tosl
+PFA_CAS2:
+ mov tosh, tosl
+ jmp_ DO_NEXT