When the POST identifies a valid ROM, it does a far call to byte
3 of the
ROM
(which should be executable code). The adapter
card may now perform its power-on initialization tasks. The
feature
ROM
should return control to the BIOS routines by
executing a far return.
Keyboard Encoding and
Usage
Encoding
The keyboard routine provided by IBM in the
ROM
BIOS
is
responsible for converting the keyboard scan codes into what will
be termed "Extended ASCII."
Extended ASCII encompasses one-byte character codes with
possible values of 0 to 255, an extended code for certain extended
keyboard functions, and functions handled within the keyboard
routine or through interrupts.
5-14
System BIOS
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