best option for terminal emulation?

Hi,

I'm teaching myself about microprocessors and microcontrollers. My
current project is building an I/O board that will use an ATMEG16 AVR
to interface a MicroVGA adaptor (http://www.dontronics-shop.com/4d-
Micro-VGA-320-Core-p-16145.html) and a PS/2 keyboard to an 8-bit data
bus. Initially I'm doing this as an Apple II bus card (so I will be
able to PEEK to get a keypress, and POKE to send a character to the
screen. But I've got a vague long term goal of eventually using it as
the terminal for a Z80 homebrew computer, and if I do build something
like that, I'd like to get it to the point it can run some flavour of
CP/M. I'm probably a year or two away from even starting the Z80
computer, but I'd like to think that the board I build now can be
usable without too many changes.

So I need to work out what the command protocol will be betwen the I/O
board and the computer it interfaces with (i.e. initially an Apple II,
eventualy the homebrew Z80). I want to avoid having a memory mapped
interface, since I don't want to have a lot of RAM on my board, and
also because that will then mean the host computer needs to do all the
work of maintaining the state of when to scroll the screen, wrap
lines, etc. And doing it on the host means I have to do it twice. So
I'd rather have the interface be a stream of commands, all POKEd to
the same memory location, and have control characters for e.g.
clearing the screen, moving the cursor to a particular location etc.

So I have the option of either inventing my own protocol and command
sequences, or emulating some existing terminal (e.g a VT100).

So my question is, is there any existing terminal that would be simple
to emulate, and would make it easy for me later on if I ever do get to
the point of using this card as the I/O for a homebrew CP/M machine?

I've done a bit of research, and found this post
http://209.85.173.104/search?q=cache:hWjZzVXIqawJ:www.groupsrv.com/computers/about54711.html
from which I inferred that there wasn't any standard, and I could just
as easily invent my own protocol, and as long as it contained commands
for the following functions, I should be able to get (for example)
Wordstar to run on it?
LEVEL (Morrow Terminal Attribute Install Levels)
CURSOR (Cursor addressing sequence, sends cursor to
Row,Column on screen)
CLR (Clear Screen)
CEOL (Clear to End of Line sequence)
CEOS (Clear to End of Screen Sequence)
RIGHT/LEFT/UP (Move Cursor)
HOME (Send Cursor to Upper Left Corner)
HI/LO (High-Light Low-Light)

Regards,

Jonno
.

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