Compaq EN Series 8.4.8 ACCESSING CMOS, 8.4.9 ACCESSING CMOS FEATURE BITS

Chapter 8 BIOS ROM
Compaq Deskpro EN Series of Personal Computers
Desktop and Minitower Form Factors
Third Edition - September 1998
8-16
8.4.8 ACCESSING CMOS
Configuration memory data can be retrieved with the BIOS call INT 15, AX=E823h. This tri-
modal function retrieves a singl e byte from th e CMOS m a p described in Chapter 4. Th e function
is described as follows:
INPUT: EAX = E823h
BH = 0, Read
= 1, Write
BL = Value to write (if a write is specified)
CX = Bytes number ( z ero-based)
OUTPUT:
(Successful)
CF = 0
AH = 00h
AL = Byte value (on a read)
(Failure)CF = 1
AH = 86h, Function not supported
= FFh, byte does not exist
8.4.9 ACCESSING CMOS FEATURE BITS
The BIOS function INT 15, AX=E845h is a tri-modal call for accessing areas in non-volatile
memory (CMOS) used for storing variables for various featur es. Note that this function di ffers
from the previously discussed call since data blocks of varying lengths are retrieved.
INPUT: EAX = E845h
BL = 0, Read
= 1, Write
BH = Value Read/to Write
CX = Feature Bits Number (refer to following description box)
DS:SI = Pointer to buffer passing multiple byte features
OUTPUT:
(Successful)
CF = 0
EAX = Reserved
BH = Value read (on a read)
(Failure)CF = 1
AH = 86h, Function not supported