SECTION 6
Conversions and Interfaces
PEN*KEY
R
6100 Computer Programmer’s Reference Guide 6-85
INT 15h, Function AH = 87h: Move Block
BIOS
Copies a block of memory from anywhere in the system address space to anyĆ
where else in the system address space. Memory space not generally available to
realĆmode programs is accessible through this function.
On Entry:
AH = 87h
CX = Number of 16Ćbit words to move
ES:SI = Pointer to 48Ćbyte GDT table allocated by calling program
On Return:
AH = 00 = Successful move
01 = RAM parity error occurred
02 = Other exception occurred
03 = Gate address line 20 failed
Carry = 0 = No error
1 = Error
When called, two of the descriptors in the GDT table specify the source and desĆ
tination addresses of the block to be moved. The BIOS builds the other four desĆ
criptors. The calling program supplies the segment limits, base address of the
data blocks, and the access rights for each location.
INT 15h, Function AH = 88h: Read Extended Memory Size
BIOS
Reads the amount of memory above 1 megabytes from the CMOS RAM locations
30h and 31h.
On Entry:
AH = 88h
On Return:
AX = Number of contiguous 1 KB blocks of extended memory
INT 15h, Function AH = 89h: Switch to Protected Mode
BIOS
GDT describes the memory management environment in effect on return to the
calling program. All table descriptors are initialized by the calling program exĆ
cept the BIOS code segment descriptor, with an access rights byte set to 9Bh.
The address is set to F0000h and the segment limit is set to 0FFFFh. The DS,
ES, and SS descriptors are loaded with 0018h, 0020h and 0028h, respectively.
The descriptors built at these GDT offsets describe the segments that these regĆ
isters reference after the BIOS returns to the calling program.
The program entering protected mode must construct its own IDT. This IDT
must not overlap the BIOS realĆmode table and must handle all interrupts while
the program is in protected mode.
On Entry:
AH = 89h
BH = Interrupt number for IRQ 0
BL = Interrupt number for IRQ 8
ES:SI = Pointer to GDT built by application
On Return:
Carry = 0 = No error
AH = 00 = Successful move
1 = Error
AH = FFh = Unsuccessful
6. Conversions and
Interfaces
Summary of Contents for PEN*KEY 6100
Page 1: ...PEN KEYR 6100 Computer PROGRAMMER S REFERENCE GUIDE P N 977 054 001 Revision B December 2000 ...
Page 14: ...CONTENTS xii PEN KEYR 6100 Computer Programmer s Reference Guide ...
Page 22: ...Preface 8 PEN KEYR 6100 Computer Programmer s Reference Guide PREFACE ...
Page 318: ...GENERAL INDEX Index 6 PEN KEYR 6100 Computer Programmer s Reference Guide ...