Divide 16 bit int by 8 bit int to 8 bit int and remainder
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| #define bf_carry 3, 0 #define bf_zero 3, 2 #define same 1 #define wreg 0 #define stc bsf bf_carry #define clc bcf bf_carry ;-[ Div ]-------------------------------------------------------------- ; Call w/: Number in f_divhi:f_divlo, divisor in W. ; Returns: Quotient in f_divlo, remainder in f_divhi. W preserved. ; Carry set if error. Z if divide by zero, NZ if divide overflow. ; Notes: Works by left shifted subtraction. ; Size = 29, Speed(w/ call&ret) = 7 cycles if div by zero ; Speed = 94 minimum, 129 maximum cycles Div; addlw 0 ; w+=0 (to test for div by zero) stc ; set carry in case of error btfsc bf_zero ; if zero return ; return (error C,Z) call DivSkipHiShift iDivRepeat = 8 while iDivRepeat call DivCode iDivRepeat-- endw rlf f_divlo, same; C << lo << C ; If the first subtract didn't underflow, and the carry was shifted ; into the quotient, then it will be shifted back off the end by this ; last RLF. This will automatically raise carry to indicate an error. ; The divide will be accurate to quotients of 9-bits, but past that ; the quotient and remainder will be bogus and carry will be set. bcf bf_zero ; NZ (in case of overflow error) return ; we are done! DivCode rlf f_divlo, same ; C << lo << C rlf f_divhi, same ; C << hi << C btfss bf_carry ; if Carry goto DivSkipHiShift; subwf f_divhi, same ; hi-=w stc ; ignore carry return ; done ; endif DivSkipHiShift subwf f_divhi, same ; hi-=w btfsc bf_carry ; if carry set return ; done addwf f_divhi, same ; hi+=w clc ; clear carry return ; done |
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| pic@canadaspeaks.com asks: " what language is this? it looks like mostly asm, but x = y and while loops are not assembly instructions." |
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James Newton replies: That is pseudo code that should be translated into the equvilent ASM code before the code is used. Please consider posting a complete version if you get the code to work. |