keyboard handler,... need a little help 
Author Message
 keyboard handler,... need a little help

Hey,
    Im trying to write a keyboard interrupt handler similar to that of
the BIOS but i dont know how to handle some of the keys.
    What do I do with combination key codes? Isnt the make code for the
combination "SHIFT F7" 0x5a?
    How do I handle extended codes? What are the extended codes? My book
says codes 85-A6 are extended, do I read a 00 first, what about the
keyboard overrun signal? I'm so confused
    Can someone outline what my keyboard handler should do to be a
viable experimental replacement for the BIOS int 09?

Thanks a lot,

Bart "The Good Guy" Trzynadlowski



Wed, 29 Aug 2001 03:00:00 GMT  
 keyboard handler,... need a little help
Quote:

> Hey,
>     Im trying to write a keyboard interrupt handler similar to that of
> the BIOS but i dont know how to handle some of the keys.
>     What do I do with combination key codes? Isnt the make code for the
> combination "SHIFT F7" 0x5a?
>     How do I handle extended codes? What are the extended codes? My book
> says codes 85-A6 are extended, do I read a 00 first, what about the
> keyboard overrun signal? I'm so confused
>     Can someone outline what my keyboard handler should do to be a
> viable experimental replacement for the BIOS int 09?

> Thanks a lot,

> Bart "The Good Guy" Trzynadlowski

Confused? I am not surprised, but be warned it's 4:30 am so I may just
as bad as the documentations that often jump from place to place( what
comes from the keyboard and what BIOS places in the keyboard buffer for
DOS to read.
All the keyboard sends is, when a key is pressed and when it is
released.
The numbers sent by the keyboard are the scan codes same as what BIOS
reports when a single key is pressed. When you press a CTL, ALT, SHIFT,
NUMLOCK SCROLLOCK and numlock  BIOS receives the key number but does not
place anything in the keyboard buffer, instead it keeps track of these
keys in another 2 bytes of BIOS data area. When another key is pressed
it uses the saved shift status to decide what ascii and scan code to
report.
For keys that do have a (printable)character associated with it the
shift status decides what character BIOS will report while the scan code

includes the tab). Keys that only have a scancode like the function keys
must be reported as a different scan code. Another think I can give you
of the top of my head is [ALT - leters] get translated by bios to same
scan but ASCII(1) and so on in alphabetical order.

Got to go, I just dozed of while thinking about hte correctness ot the
message.



Thu, 30 Aug 2001 03:00:00 GMT  
 keyboard handler,... need a little help
|For keys that do have a (printable)character associated with it the
|shift status decides what character BIOS will report while the scan code

That depends on what keyboard driver you have. They're all numbers

german driver has the y somewhere else (z?), etc...



Thu, 30 Aug 2001 03:00:00 GMT  
 keyboard handler,... need a little help

Quote:


> |For keys that do have a (printable)character associated with it the
> |shift status decides what character BIOS will report while the scan code

> That depends on what keyboard driver you have. They're all numbers

> german driver has the y somewhere else (z?), etc...

Details, details.
What do you mean driver are you talking in Win95 environment?
The default key mapping is decided by a table in BIOS unless int 9 is
replaced or things have changed on the Pentium platform and those new
keyboards do not just report a scancode. Driver would replace the INT9
handler or it's table if possible.
I think the difference between keyboards ( languagewise ) is in the
labels on the keys and different table in bios(and occasionaly key in a
different place ,) the scan codes are mostly the same.
(Just a speculation.


Sat, 01 Sep 2001 03:00:00 GMT  
 
 [ 4 post ] 

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