Subject: Re: div by 10 on Z80 was RE: Reading Polymorphic

Hi chuck I think the restore operation will cause a carry meaning I need to clear it here with something like: ora a ; or other carry clearing instruction If someone has a debugger running, they might check this but it does look as though the SBC will cause a carry that needs to be cleared. The result of the add hl,de that didn't create a carry left a negative number that will be modified back to a positive number with a subtract. I'm relatively sure that creates a carry. Still, it removes one instruction from the outer loop which is 4 cycles time 7. That is 28 clocks! This is great. Fine tuning this has been fun. div10: xor a ld de,0fd80h ; largest power of 2 times 10 less then 800d ld b,07 ; only seven loops needed to finish divide 80 divloop: add hl,de ; trial subtract jr c,div10s1 ; carry means trial passed sbc hl,de ; undo previous add, carry is set?? ora a ; clears carry div10s1: rl a add hl,hl ; shift number to reuse same constant, 640 decimal djnz divloop add hl,hl ; push full remainder in HL ret Dwight _________________________________________________________________ Shed those extra pounds with MSN and The Biggest Loser! http://biggestloser.msn.com/