Chapter
3.
Instruction
Set
JZ
LOA
3-32
The AND immedidte instruction
in
block ONE zeroes
all
hils
of
the ddta
byte
except
the
Sign bit, which re-
maim
unchanged.
If
the Sign bit
WdS
1ero, the Zero
condition
bit
will
he
set, and the JZ instruction will cause
progrdm
control
to
be trdnsferred tu the instruction dt PLUS. Otherwi.,e, the JZ
in,truction
will merely
update
the progrdm
counter
hy
three, dnd the JNZ instruction
will
he
executed,
causing control to
be
transferred
to
the
instruction
at MINUS. (The Zero bit
is
undffected by
dll
jump instructions.)
The RLC instruction
in
block
TWO
cau,e,
the Carry bit tu be set equal to the Sign bit of the data byte. If the
Sign bit was reset,
the JNC instrllction causes a iump
To
PLUS. Otherwise the JMP instruction
is
executed,
unconditionally transferring control to MINUS. (Note that,
in
thi'i instdnce, a
JC
instruction could
he
suh-
'itituted
for the unconditional iump with identical results.)
The add immedidte instruction
in
block
THREE
causes the
condition
hits to be set.
If
the sign bit was set, the
J M instruction
Cd
uses program control
to
he
trdnsferred to MINUS. Otherwise, program
control
flows auto-
mdtically
into the PLUS routine.
JUMP
IF
ZERO
The JZ instruction te.,ts the '>etting
of
the zero tllg. If the
fldg
is
set to one, program
execution
resumes
at
the
dddres'i specified
in
the JZ instruction.
If
the flag i, reset
to
lero,
execution
continues
with the next sequentidl
ins tr
uc
t ion.
Op
co
de
Operand
JZ
The address may
he
specified as a number, d label, or
dn
expre<,sion. The dssemhler
invert<;
the high dnd low
address bytes when it
assemble'i the instruction.
Example:
o 0
o
o
Cycles:
States:
Addre<"ing:
Flags:
low addr
high addr
3 (2 or 3
(In
8085)
10
(7
or
10
on 8085)
immediate
none
EXMnple.,
of
the vdridtions
of
the iump instruction dPpear
in
the description
of
the JPO instruction.
LOAD
ACCUMULATOR
DIRECT
LDA loads the accumuldtor with a copy
of
the
byte
at the location specified
in
bytes two and three
of
the
LDA instruction.
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