boot serial console speed

Ruslan Ermilov ru at freebsd.org
Sun Nov 14 01:39:13 PST 2004


On Sun, Nov 14, 2004 at 10:39:13AM +0200, Danny Braniss wrote:
> what's the magic encantation to set the console to 38400?
> btw, i solved my problem by just commenting out that part of the code,
> since i rely on the bios setting it.
> 
> from src/sys/boot/i386/boot0/Makefile:
> 
> # Comm settings for boot0sio.  0xE3 => 9600 8-N-1
> # XXX: We should create a build-tool or something to convert BOOT_CONSOLE_SPEED
> # and BOOT_COMCONSOLE_PORT into the correct values to define on the build
> # command line
> BOOT_BOOT0_COMCONSOLE_SPEED?=	0xE3
> 
This is the value passed in the AL register to the Int 14/AH=00h
BIOS function:

	http://www.ctyme.com/intr/rb-0811.htm

: Bit(s) Description     (Table 00300)
: 7-5    data rate (110,150,300,600,1200,2400,4800,9600 bps)
: 4-3    parity (00 or 10 = none, 01 = odd, 11 = even)
: 2      stop bits (set = 2, clear = 1)
: 1-0    data bits (00 = 5, 01 = 6, 10 = 7, 11 = 8)

0xE3 = 111-00-0-11 = 9600 bps, no parity, 1 stop bit, 8 data bits

But I think it's not possible to set it to anything above 9600 bps
using this BIOS call.


Cheers,
-- 
Ruslan Ermilov
ru at FreeBSD.org
FreeBSD committer
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