Re: Stored data missed in setup.S

["Randy.Dunlap" <rddunlap@osdl.org>]

On Wed, 23 Apr 2003 10:36:55 -0400 (EDT) "Richard B. Johnson" <root@chaos.analogic.com> wrote:

| On Wed, 23 Apr 2003, Andrew Kirilenko wrote:
| 
| [SNIPPED...]
| 
| > OK. And now code looks like:
| > -->
| > start_of_setup: # line 160
| > 	# bla bla bla - some checking code
| >         movb    $1, %al
| >         movb    %al, (0x100)
| > ....
| > ....
| > 	cmpb    $1, (0x100)
| > 	je bail820 # and it DON'T jump here
| > <--
| >
| 
| > I'm sure, I'm doing something wrong. But what???
| 
| The only possibiity is that the code you just showed is not
| being executed. Absolute location 0x100 is not being overwritten
| by some timer-tick (normally) so whatever you write there should
| remain. You just put a byte of 1 in that location and then
| you compared against a byte of 1. If the CPU was broken, you
| wouldn't have even loaded your code.

Could possibly be that DS (seg register) is altered between
the store and the comparison...

| It is quite likely that the IP is being diverted around your code
| by some previous code.
| 
| FYI, you can check the progress of your code by 'printing' on
| the screen. Set up ES to point to the screen segment, and write
| letters there:
| 
| 	movw	$0xb800, %ax
| 	movb	%ax, %es
| 	movb	$'A', %es:(0)
| 
| This 'prints' an 'A' at the first location on the screen.


--
~Randy