AMD Am186 Series, Instruction Set

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Instruction Set 4-80
JAE Jump If Above or Equal JAE
JNB Jump If Not Below
JNC Jump If Not Carry
What It Does
If the previous instruction clears the Carry Flag (CF), JAE, JNB, and JNC stop executing
the current sequence of instructions and begin executing a new sequence of instructions;
otherwise, execution continues with the next instruction.
Syntax
Description
JAE, JNB, and JNC test the flag set by a previous instruction. The terms above and below
indicate an unsigned number comparison. If the given condition is true, a short jump is
made to the location provided as the operand.
Operation It Performs
Flag Settings After Instruction
Form Opcode Description
Clocks
Am186 Am188
JAE rel8 73 cb Jump short if above or equal (CF=0) 13,4 13,4
JNB rel8 73 cb Jump short if not below (CF=0) 13,4 13,4
JNC rel8 73 cb Jump short if not carry (CF=0) 13,4 13,4
JAE label
To jump if the result of a previous unsigned
comparison was above or equal, use JAE
or one of its synonyms, JNB or JNC. Each
form performs the same operation.
JNB label
JNC label
if (CF == 0)
{
/* extend sign of label */
if ( label < 0)
displacement = 0xFF00 |
label;
else
displacement = 0x00FF & label;
/* branch to labeled instruction */
IP = IP + displacement;
}
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 –