AMD Am186 Series, Instruction Set

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Instruction Set 4-19
BOUND*Check Array Index Against Bounds BOUND
What It Does
BOUND determines whether an integer falls between two boundaries.
Syntax
Description
BOUND ensures that a signed array index is within the limits specified by a block of memory
between an upper and lower bound. The first operand (from the specified register) must
be greater than or equal to the lower bound value, but not greater than the upper bound.
The lower bound value is stored at the address specified by the second operand. The upper
bound value is stored at a consecutive higher memory address (+2). If the first operand is
out of the specified bounds, BOUND issues an Interrupt 5 Request. The saved IP points
to the BOUND instruction.
Operation It Performs
Flag Settings After Instruction
* – This instruction was not available on the original 8086/8088 systems.
Form Opcode Description
Clocks
Am186 Am188
BOUND
r16,m16&16
62
/r
Check to see if word register is within bounds 33–35 33–35
BOUND index,bounds
if (( index < [bounds]) || (index > [ 2]))
/* integer is outside of boundaries */
interrupt(5);
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Processor Status
Flags Register
reserved
OF DF IF TF SF ZF AF PF CF
? = undefined; – = unchanged
– – – – – – res – res – res –