8
All and more about Sharp PC-1500
at
http://www.PC-1500.info
2-2-2. Internal registers
Symbol
Name Bit si
ze
ocsc1iptlon
p
P
rogr
arn C<
ninter
16 I
ndi
cates the
addr
ess ne
xt
to the ;)(!dre
ss
t
he
CPU
is
no\•1
in exe
cution
II
wi
ll
be
in
cremen1ed
by
" 1-
'..
'
Jhe
n t
ho
next instruc
li
on
is
1e1
c::ho
<f
.
s
s~a
c
k
16
l
ndi
ca
1cs
th
e st
ack
a
ddr
ess.
p
oir
nc'
A A ccv m
ul
atoc
s Used t
or
retenti
on
of
c
p.
eral
iona
l
<e
su
ll
or
for data
!rans.fe r •v
il
h
th
e e
x1
c r
na
1
mcrnofy
.
Xrc
g
XL 8
XL.
XH
. YL
.YH
.
Ul
.
UH
compris-e ind
ependen;
8·
XH
8
b
it
re
giste
rs.
Also. used as 1&.b
it
data poin;ers. x rcg. Yrcg. and
YL
I
8
Ur
cg .
.....
hen
used in a pair.
Y
reg
YH
Oeta regist
er
8
UL 8
Ur
eg
UH
8
TM
Timer
co
un
1c
r
9
v.
1
hen
'
'O.,
is s
et
to
!he
T
M.
it steps t
he
c
oun
ler
ac~
1
on
.
Whc
r' a
n;•th
1ng Olhcr lh an "O ..
is
SCI. 1;
p
uts
the counter into ac?ion. When the
TM
lu
~
ns
fu
ll
of
..
1·· ·
11it
h
ti'~
in1
euu
pt
e
nab
le sig n
<)
l
IE
on
.
CPU executes an 1
ntcrtup
1 p
roc
essi
ng
.
PU
1 Genefal Pt•rpose
fl
ip-Hep.
PV
1
DI
SP
1 LCO
oo
/ o
lf
co
1
nro
1.
T S
1;;.
1o
s
re~1
i
st
et
8
LO\v otdef 5 b
it
s fOpfes
an1
one of f1\'C s
ta
tus of
opeta11o
na
l result
2-2-3. Status flags
S1
at
us
fl
a
g
~
.
C. \'.
f~.
Z. 1
1'
·:
a
rc
c<u1ta
in
cd
in
the 8-bit st
atu
s
re
gist
er
.
In
gene
ral
.
tl
a
g.'\(
Hhcr
than
IE
change their scatc
af
ter the execution of
ar
it
h
£n
etical instructio
n.
Status register T = [ 0 ' 0 I 0 H I V Z j 1 E C I
(i) Ca:rry flag c
Cat"ry flag C is set \vhcn there is <' carry f
ro
n1
t
l1i:
MS ll and r
cs
t.:t
\vh
r,;
11 there
is
n<>
carry.
~
:
o
..
Sl
JBTR.
t\Cl
', the
nag
is
:se
t \
Vh
Cn t
he
re is no borrO\V or r
l'f\C
t \Vht n
th
ere is.
<D
Ha
If
carry flag H
Half ca
rr
y
lla
g H
is
se
t when there is a carry
from
the bit position "3" (digit-to-
dig
it
ca
r
.ry)
a
nd
reset \vhcn t
he
re is no ca
l'
ry
.
<D
Zero
flag Z
Zero
nag
z is s
r:
t
\Vhc
n the
()p
er'ational
l'
C'S
llh
is
7Cl'
O anti
re
set \\
-'
hen
n<H
.
©
Overflow
flag V
Overn
ow
na
g V is
se
t or r
ese
t d
epe
n
din
g on the op
era
ti
onal r
es
u
lt
of
.. C6
<:b
CT:
where.
the c
ar
ry from the bit position 6
of
a single b
yt
e data
is
a
ss
umed
to
b
~
C6
and
t
h c
carr~
·
fr
om
the bit pos
iti
on 7 to be C7.
Single
by
te
da
ta
87
9695
94
9382
8 1
BO
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