Specifications

AMD Geode™ GeodeROM Functional Specification 203
Video BIOS Support
32087C
13.2.11 Function 0Ah: Return VBE Protected Mode Information
Description:
Calling this function returns a real mode pointer (segment:offset) to the protected mode interface table. The table
points to code that can be copied into an application’s memory space for execution from a 32-bit code segment. These
functions execute a near return (“retn”) when returning to the calling application.
Table Offset Description
00h Offset to code for Set Bank Function (05h), Subfunction 00h
02h Offset to code for Set Display Start Function (07h), Subfunctions 00h and 80h
04h Offset to code for Set Primary RAMDAC Data (09h), Subfunction 00h
06h Offset to table of ports and memory locations sub-table
Applications must still set the registers the same way they would for an INT 10h call, including the AX register. The Dis-
play Start Function (07h) is slightly different when called from the protected mode function. Instead of specifying the
pixel and scan line position, DX:CX specifies the display start address in bytes.
The ports and memory locations sub-table provides a list of I/O addresses and memory locations that may be needed
by an application for I/O privilege or read/write permission. The sub-table is an array of WORD values terminated by
0FFFFh for the I/O locations immediately followed by a second array of DWORD values for memory locations and a
WORD value for the length of memory needed. The second array is also terminated by the WORD 0FFFFh for the
memory locations. Note that a memory location CAN NOT use 0FFFFh as the low order WORD in its address. If no
addresses are needed then the table will contain two entries, each a WORD of 0FFFFh.
Passed:
Returns:
Parameter Description
AH 4Fh
AL 0Ah
BL 00h
Parameter Description
AX VBE return status
CX Length of table
ES:DI Real mode pointer to table