Instruction Set
4-119
JO
Jump If Overflow
JO
What It Does
If the previous instruction sets the Overflow Flag (OF), JO stops executing the current
sequence of instructions and begins executing a new sequence of instructions; otherwise,
execution continues with the next instruction.
Syntax
Description
JO tests the flag set by a previous instruction. If the given condition is true (OF=1), a short
jump is made to the location provided as the operand.
Operation It Performs
Flag Settings After Instruction
Tips
If you need to jump to an instruction at
farlabel that is more than 128 bytes away, use the
following sequence of statements:
JNO nearlabel
; This does the equivalent of a long jump
JMP farlabel
; based on the JO condition.
nearlabel:
Form
Opcode
Description
Clocks
Am186 Am188
JO
rel8
70
cb
Jump short if overflow (OF=1)
13,4
13,4
JO
label
To jump if the result of a previous
operation set OF to 1, use JO.
if (OF == 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...