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-rw-r--r--amforth-6.5/avr8/words/umstar.asm37
1 files changed, 37 insertions, 0 deletions
diff --git a/amforth-6.5/avr8/words/umstar.asm b/amforth-6.5/avr8/words/umstar.asm
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+; ( u1 u2 -- d)
+; Arithmetics
+; multiply 2 unsigned cells to a double cell
+VE_UMSTAR:
+ .dw $ff03
+ .db "um*",0
+ .dw VE_HEAD
+ .set VE_HEAD = VE_UMSTAR
+XT_UMSTAR:
+ .dw PFA_UMSTAR
+PFA_UMSTAR:
+ movw temp0, tosl
+ loadtos
+ ; result: (temp3*temp1)* 65536 + (temp3*temp0 + temp1*temp2) * 256 + (temp0 * temp2)
+ ; low bytes
+ mul tosl,temp0
+ movw zl, r0
+ clr temp2
+ clr temp3
+ ; middle bytes
+ mul tosh, temp0
+ add zh, r0
+ adc temp2, r1
+ adc temp3, zeroh
+
+ mul tosl, temp1
+ add zh, r0
+ adc temp2, r1
+ adc temp3, zeroh
+
+ mul tosh, temp1
+ add temp2, r0
+ adc temp3, r1
+ movw tosl, zl
+ savetos
+ movw tosl, temp2
+ jmp_ DO_NEXT