Intel 80286 User Manual

NUMERIC PROGRAMMING EXAMPLES
i CALCULATE OFFSET INTO JUMP TABLE
MOV BH,O i CLEAR UPPER HALF OF BX,
MOV Bl,AH i lOAD CONDITION CODE INTO BL
AND BL,OOOOOIIIB i ALL BITS EXCEPT C2-CO
AND AH,01000000B i CLEAR ALL BITS EXCEPT C3
SHR AH,2 SHIFT C3 TWO PLACES RIGHT
SAL BX,1 SHIFT C2-CO 1 PLACE LEFT (MULTIPLY
BY 2)
OR Bl,AH DROP C3 BACK IN ADJACENT TO C2
(OOOXXXXO)
i JUMP TO THE ROUTINE 'ADDRESSED' BY CONDITION CODE
JMP FXAM_TBLIBXl
HERE ARE THE JUMP TARGETS, ONE TO HANDLE
i EACH POSSIBLE RESULT OF fXAM
PO LU N NOR M :
POS_NAN:
N E LU N NOR M :
N E
LN AN:
PO LN 0 RM:
POLINFINITY:
N E LH 0 RM:
NELINFINITY:
PO LZ E: R 0:
EMPTY:
NELZERO:
PO LDE H 0 RM:
HELDENORM:
Figure 4-2. Conditional Branching for FXAM (Cont'd.)
EXCEPTION HANDLING EXAMPLES
There are many approaches to writing exception handlers. One useful technique is to consider the
exception handler procedure
as consisting of "prologue," "body," and "epilogue" sections of code. (For
compatibility with the 80287 emulators, this procedure should be invoked by interrupt pointer (vector)
number 16.)
4-3
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Intel 80286 Specifications

General

Processor Type	Microprocessor
Clock Speed	6 MHz to 25 MHz
Transistor Count	134, 000
Addressable Memory	16 MB
Instruction Set	x86
Architecture	x86
Data Bus Width	16-bit
Address Bus Width	24-bit
Operating Modes	Real mode, Protected mode
Process Technology	1.5 µm
Voltage	5V
Introduced	1982
Package	68-pin PGA