Beefy Boxes and Bandwidth Generously Provided by pair Networks
more useful options

Re: Re: Re: Z80 Assembler Questions

by dpuu (Chaplain)
on Jan 31, 2003 at 18:17 UTC ( #231677=note: print w/replies, xml ) Need Help??

in reply to Re: Re: Z80 Assembler Questions
in thread Z80 Assembler Questions

I remember the first Z80 assembler I wrote, about 20 years ago. Back then we had very limited resources (on the computer), so were forced to do a fair amount of work on paper.

The way to identify the construction of the instruction formats is to create a 16x16 grid (for each hex digit in the basic instructions). When you place the instructions on this grid it will become very obvious how the instructions are structured. You'll even see how the designers used a few meaningless instructions (e.g. ld a,a) to find encodings for other instructions (e.g. HALT). Once you've done the basic instructions, overlay the extention opcode tables: you'll find that the IX/IY instructions closely map onto the HL/DE register instructions. You'll also find that you can guess a few "undocumented" instructions in the CB extention set -- there's one empty column, IIRC).

I've sorry I can't remember more of the details: it was a long time ago, and I'm suddenly feeling old. --Dave

Log In?

What's my password?
Create A New User
Node Status?
node history
Node Type: note [id://231677]
[1nickt]: erix perhaps you could kindly point out your technique to roho and everyone will be happy.
[Discipulus]: but i'm also animalist, so i' hirted by 1nickt's sig: The way forward always starts with a mammal test... grin..
[erix]: I might if I did remember. It's probably somewhere in the site docs
[uhClem]: I don't favor that sort of thing around here but the place for our politics is wherever we live.
[uhClem]: And besides, the objection to it was off-topic.
[Discipulus]: 1nickt hide signature is a positive action; i think is not a solution here
[erix]: my objection to sigs is just that they take screen space. ( Some monks would have *several* slogans underneath a 1-liner reply )

How do I use this? | Other CB clients
Other Users?
Others musing on the Monastery: (11)
As of 2017-06-22 12:36 GMT
Find Nodes?
    Voting Booth?
    How many monitors do you use while coding?

    Results (519 votes). Check out past polls.