Instruction Set
4-126
JS
Jump If Sign
JS
What It Does
If the previous instruction sets the Sign Flag (SF), JS stops executing the current sequence
of instructions and begins executing a new sequence of instructions; otherwise, execution
continues with the next instruction.
Syntax
Description
JS tests the flag set by a previous instruction. If the given condition is true (SF=1), 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
JS
rel8
78
cb
Jump short if sign (SF=1)
13,4
13,4
JS
label
To jump if the result of a previous
operation set SF to 1, use JS.
if (SF == 1)
{
/* 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 –
Содержание Am186 Series
Страница 1: ...Am186 and Am188 Family Instruction Set Manual February 1997...
Страница 10: ...Table of Contents x...
Страница 18: ...Programming 1 8...
Страница 40: ...Instruction Set Listing 3 14...