One byte or nybble at a time. Check out instructions that set and use the carry flag.

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We never have time to do it right; but we always have time to do it over.

 

Its handles larger numbers the same way you do when not using a calculator. ie: When doing addition on paper, you will only deal with single digits at a time and use "carries" to move the values in excess of 9 to the column on the left:

56 + 37 =??

6 + 7 = 13
So keep the 3 in the units column and add the 1 to the 5 & 3 in the 10s column ( 5 + 3 + 1carry = 9 ) so the answer is 93. The 8 bit processor program has to do the same thing except it only has to carry when the answer exceeds 255 (For unsigned math) or 127 (For signed math).
Funny thing on this topic is that I only really learned math once I started writing assembler: I'd never thought about the fact that multiplication is just a form of addition. ie: You can figure out 7 x 13 just by adding 13 to itself 7 times. Too much emphasis on just memorizing multiplication tables when I was growing up I guess.

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--- The days of the digital watch are numbered. ---

 

Aaah... that sounds simple!

Does anyone know of any books (free would be nice... as in ebooks, but not a requirement) that i can get to read up on z80 Assembly? I understand what most of the op codes do, but there are a few that i can't figure out what their purpose is...

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There is no "I" in "team", unless Apple makes it... Then it would be iTeam.

 

If you don't understand it, you probably don't need to know about it - a 16F PIC has only 35 instructions, and probably a third of those are only very rarely used (some I've NEVER used!).

As always, build one, and play with it - rather than keep asking silly questions!.

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PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

Why don't you go to the Z80 support website and get whatever information is available?

Zilog Z80 CPU user manual and other related infos

For those OP codes that troubles you, you can then ask here.

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L.Chung

 

Is my name Marks35? No. It is Marks256!

I like silly questions.

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There is no "I" in "team", unless Apple makes it... Then it would be iTeam.