7 stack and stack pointer, 1 stack, Toshiba – Toshiba TMP87CP24AF User Manual
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TOSHIBA
TMP87CM24A/P24A
Example: BCD operation
(The A becomes 4?H after executing the following program when A =
19
h
,
B =
28
h
)
ADD
A, B
; A<-41
h
, HF<-1,CF<-0
DAA
A
;
A
41H + 06
h
= 4?H (decimal-adjust)
(4) Jump status flag (JF)
Zero or carry information is set to the JF after operation (e. g. INC, ADD, CMP, TEST).
The
JF
provides
the
jump
condition
for
conditional
jump
instructions
[JRS
T/F,
$-F2-hd],
[JR
T/F,
$ -F 2 -hd] (T or F is a condition code). Jump is performed if the JF is "1" for a true condition (T), or the
JF is "0" for a false condition (F).
The
JF
is
set
to
"1"
after
executing
the
load/exchange/swap/nibble
rotate/jump
instruction,
so
that
[JRS T, $
-F
2
-F
d] and [JR T, $
-
f
2
-
f
d] can be regarded as an unconditional jump instruction.
Example : Jump status flag and conditional jump instruction
; Jump when a carry is caused by the immediately
preceding operation instruction.
; JF is set to "1" by the immediately preceding
instruction, making it an unconditional jump
instruction.
INC
A
JRS
T, SLABLE1
LD
A,(HL)
JRS
T, SLABLE2
Example
:
The
accumulator
and
flags
become
as
shown
below
after
executing
the
following
instructions
when the WA register pair, the HL register pair, the data memory at address OOCS
h
, the carry flag
and the half carry flag contents being
"219A
h
",
"OOCS
h
",
"D7
h
",
"1" and "0", respectively.
Instruction
Acc. after
execution
Flag after execution
JF
ZF
CF
HF
ADDC
A, (HL)
72
1
0
1
1
SUBB
A, (HL)
C2
1
0
1
0
CMP
A, (HL)
9A
0
0
1
0
AND
A, (HL)
92
0
0
1
0
LD
A, (HL)
D7
1
0
1
0
ADD
A, 66H
00
1
1
1
1
Instruction
Acc. after
execution
Flag after execution
JF
ZF
CF
HF
INC A
9B
0
0
1
0
ROLC A
35
1
0
1
0
RORC A
CD
0
0
0
0
ADD WA,0F508H
16A2
1
0
1
0
MUL W, A
13DA
0
0
1
0
SET A.5
BA
1
1
1
0
1.7
Stack and Stack Pointer
1.7.1 Stack
The
stack
provides
the
area
in
which
the
return
address
or
status,
etc.
are
saved
before
a
jump
is
performed
to
the
processing
routine
during
the
execution
of
a
subroutine
call
instruction
or
the
acceptance
of
an
interrupt.
On
a
subroutine
call
instruction
[CALL
a]/[CALLP
n]/[CALLV
n],
the
contents
of
the PC (the return address) is saved; on an interrupt acceptance, the contents of the PC and the PSW are
saved
(the
PSW
is
pushed
first,
followed
by
PC
h
and
PC
l
).
Therefore,
a
subroutine call
occupies
two bytes
on the stack; an interrupt occupies three bytes.
When
returning
from
the
processing
routine,
executing
a
subroutine
return
instruction
[RET]
restores
the
contents
to
the
PC
from
the
stack;
executing
an
interrupt
return
instruction
[RETI]/[RETN]
restores
the
contents to the PC and the PSW (the PC
l
is popped first, followed by PC
h
and PSW).
The
stack
can
be
located
anywhere
within
the
data
memory
space
except
the
register
bank
area,
therefore the stack depth is limited only by the free data memory size.
3
-
24-14
2002
-
10-03