[LispM-Hackers] Serial port progress

[John Morrison]

Hi;

If you don't care about the bare iron port, you can skip this message.

(1) My funky cable works.

(2) I have managed to spit out characters first from Linux, and then
from my own e3 program, and see them in minicom on my development box.

(3) I am only doing output, not input (yet?).

(4) Since I'm only doing output, I haven't screwed around with
enabling interrupts for the UART.

Coupl'a observations:

(a) The PC is an ugly, ugly piece of work.  If I had a dog that looked
like that, I'd shave it's ... and make it walk backwards.

(b) I used the BIOS to set baud rate and other things before I jump to
protected mode.

(c) The CPU can pump data at the UART way faster than it can handle
it.  I have not explored checking the various registers (I/O ports) to
see when it's ready for another char.  I assume that I can deduce this
from the I/O ports.  I will probably just busy wait.  This will
resurrect the old UNIX "nothing runs while the kernel printfs"
artifact.

On another note, I needed to do this because I was having trouble with
the SVGA stuff -- in particular, writing past the end of the first
memory bank.  This should make it easier to debug.

-jm

-- 
==== John Morrison
==== MAK Technologies Inc.
==== 185 Alewife Brook Parkway, Cambridge, MA 02138
==== http://www.mak.com/
==== vox:617-876-8085 x115
==== fax:617-876-9208
==== jm@mak.com