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 Post subject: U* and U/
PostPosted: Tue Jul 30, 2024 7:41 pm 
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Joined: Sat Jun 22, 2024 6:21 am
Posts: 14
I have implemented these words for U* and U/ in figforth 6502.
When I try $100 $10 U* the answer is $0, the same with U/.
Are the routines correct?

Thanks for any help.
Jan



[code];
; U*
; SCREEN 23 LINE 1
;
L386 .BYTE $82,"U",$AA
.WORD L365 ; link to CMOVE
USTAR .WORD *+2
LDA 2,X
STA N
STY 2,X
LDA 3,X
STA N+1
STY 3,X
LDY #16 ; for 16 bits
L396 ASL 2,X
ROL 3,X
ROL 0,X
ROL 1,X
BCC L411
CLC
LDA N
ADC 2,X
STA 2,X
LDA N+1
ADC 3,X
STA 3,X
LDA #0
ADC 0,X
STA 0,X

L411 DEY
BNE L396
JMP NEXT
;
; U/
; SCREEN 24 LINE 1
;
L418 .BYTE $82,"U",$AF
.WORD L386 ; link to U*
USLAS .WORD *+2
LDA 4,X
LDY 2,X
STY 4,X
ASL A
STA 2,X
LDA 5,X
LDY 3,X
STY 5,X
ROL A
STA 3,X
LDA #16
STA N
L433 ROL 4,X
ROL 5,X
SEC
LDA 4,X
SBC 0,X
TAY
LDA 5,X
SBC 1,X
BCC L444
STY 4,X
STA 5,X
L444 ROL 2,X
ROL 3,X
DEC N
BNE L433
JMP POP/code]


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 Post subject: Re: U* and U/
PostPosted: Tue Jul 30, 2024 11:46 pm 
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Joined: Fri May 05, 2017 9:27 pm
Posts: 895
U* takes two unsigned single numbers and returns an unsigned double number result. With the numbers $100 and $10 the high cell of the result will be zero.
Likewise, U/ takes a double number unsigned dividend and a single number unsigned divisor. It returns a single number unsigned remainder and quotient


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 Post subject: Re: U* and U/
PostPosted: Wed Jul 31, 2024 12:08 am 
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Joined: Fri May 05, 2017 9:27 pm
Posts: 895
If you are going to use the multiply and division routines from Fig-Forth, you might want to read this post on carry problems in U* and U/.


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