;Division of 16bit by 8 bit with a result in Q16.16 form ; ; X_Int.X_Frac = X_Int / Y ; ; RAM - 6 bytes (1 temp): ; X_Int = X_IntH:X_IntL 16 bit input/ output integer part ; X_Frac = X_FracH:X_FracL 16 bit output fractional part ; Y divisor / temporary ; Counter counter ; ; Size = 39 instructions ; Execution time = 6+16*15-2+3+16*15-2+3+3(return) ; = 491 instruction cycles ; ; 8-July-2000 by Nikolai Golovchenko ; 16-February-2001 fixed, reduced execution time and temporaries Div16by8to16_16 clr X_FracL clr X_FracH mov W, #16 mov Counter, W mov W, Y ;keep Y value in accumulator clr Y ;and use Y register as temporary ;Find integer part Div16by8to16_16a rl X_IntL ;shift next msb into temporary rl X_IntH rl Y rl Counter ;carry has 9th bit of temporary ;copy carry to counter sub Y, W ;substract Y (in w) from temporary snc ;if no borrow, set Counter.0 setb Counter.0 sb Counter.0 ;if Counter.0 clear (borrow) restore temporary add Y, W clc ;restore counter rr Counter ;at this point carry is the next bit of result decsz Counter ;repeat 16 times to find integer part jmp Div16by8to16_16a ;shift last integer bit rl X_IntL rl X_IntH ;Find fractional part setb Counter.4 ;Counter = 16 Div16by8to16_16b ;Shift zero bit into temporary rl X_FracL rl X_FracH rl Y rl Counter ;carry has 9th bit of temporary ;copy carry to counter sub Y, W ;substract Y(in w) from temporary snc ;if no borrow, set Counter.0 setb Counter.0 sb Counter.0 ;if Counter.0 clear (borrow) restore temporary add Y, W clc ;restore counter rr Counter decsz Counter ;repeat 16 times jmp Div16by8to16_16b ;shift last fractional bit rl X_FracL rl X_FracH mov Y, W ;restore divisor retp
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