My 2 cents on bootstrap loaders.

[Eddie Matejowsky <e.matejowsky@xxxxxxxxxx>]

There has been a bit of talk here about putting a bootstrap loader into the
f21 on chip rom. I'm crossing my fingers really hard that this happens. All
the micros I've used in the last 5 to 10 years have had this feature in one
form or another. The transputer, 68hc11, 68hc16 and 68hc12 (soon) can all
be bootstraped and run remotely. The hc11 is the only out of these 4 chips
that can use a standard pc com port, the hc16 could be done via a printer
port but the transputer and hc12 need extra hardware. The c11 system
doesn't provide the debuging features of it's big brothers, all you can do
is download 256 bytes of program/data starting at address 0000 (usually
@1200db) and/or execute the code at 0000. Extra debuging commands are nice
but I can live without them.
Anyway to get to the point. I think the minimum requirement for a boot
strap is to load a fixed sized program into a fixed location at a fixed
baudrate and then jumping to a fixed location to execute it. There also
needs to be a way to disable the bootstrap so a normal reset can happen
(such as testing for a break on the serial line).
Any extras such as memory peek/poke, variable baudrate, program length,
program location, program execute address or feedback during loading can to
done away with if rom size is an issue.
So how much rom does it take to do a serial uart (input only), input say 1k
bytes, stick them into memory and execute?
I suspect not very much, it might even fit the current sized rom (but I've
forgotten how big that is).
Eddie,
Edward Matejowsky - Queensland University of Technology (Brisbane, Australia)
personal home page at http://www.ozemail.com.au/~eddiema/index.html