Accessing Cmos; Accessing Cmos Feature Bits - Compaq iPAQ 1.0 Technical Reference Manual

Chapter 8 BIOS ROM

8.3.7 ACCESSING CMOS

Configuration memory data can be retrieved with the BIOS call INT 15, AX=E823h. This tri-
modal function retrieves a specific byte from the CMOS map described in Chapter 4. The function
is described as follows:
INPUT:
EAX
BH
BL
CX
OUTPUT:
(Successful)
CF
AH
AL
(Failure)
CF
AH

8.3.8 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 features. Note that this function differs
from the previously discussed call since data blocks of varying lengths are retrieved.
INPUT:
EAX
BL
BH
CX
DS:SI
OUTPUT:
(Successful)
CF
EAX
BH
(Failure)
CF
AH
8-8 Compaq iPAQ Series of Desktop Personal Computers
= E823h
= 0, Read
= 1, Write
= Value to write (if a write is specified)
= Bytes number (zero-based)
= 0
= 00h
= Byte value (on a read)
= 1
= 86h, Function not supported
= FFh, byte does not exist
= E845h
= 0, Read
= 1, Write
= Value Read/to Write
= Feature Bits Number (refer to Table 8-2)
= Pointer to buffer passing multiple byte features
= 0
= Reserved
= Value read (on a read)
= 1
= 86h, Function not supported
Review Copy - January 2001