Intel 80286 User Manual

NUMERIC PROGRAMMING EXAMPLES
ASSUME INITIALIZED
REENTRANT PROC
SAVE CPU REGISTERS, ALLOCATE STACK SPACE FOR
80287 STATE IMAGE
PUSH BP
MOV BP,SP
SUB SP,94
SAVE STATE, LOAD NEW CONTROL WORD,
FOR COMPLETION, ENABLE CPU INTERRUPTS
FNSAVE [BP-941
FLDCW LOCAL_CONTROL
S T I
APPLICATION EXCEPTION HANDLING CODE GOES HERE.
AN UNMASKED EXCEPTION GENERATED HERE WILL
CAUSE THE EXCEPTION HANDLER TO BE REENTERED.
IF LOCAL STORAGE IS NEEDED, IT MUST BE
ALLOCATED ON THE CPU STACK.
CLEAR EXCEPTION FLAGS IN STATUS WORD
RESTORE MODIFIED STATE IMAGE
MOV BVTE PTR [BP-921, OH
FRSTOR [BP-941
DE-ALLOCATE STACK SPACE, RESTORE CPU REGISTERS
MOV SP,BP
POP BP
RETURN POINT OF INTERRUPTIOH
IRET
REENTRANT ENDP
Figure 4-5. Reentrant Exception Handler
4-6
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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