Block Diagram - Radio Shack 26-3501 Service Manual

System
configuration
(see
the
s/stem block diagram)
The
system
consists
of
(he following components:
1.
CPUI(SC43I77)«
I
2.
CPUU(SC43l7S)x
I
3.
4K-bltRAM(rOM4)*x3)
4.
Display chip (SC43I23 «
3.
with
Duilt-in
RAN)
5.
2ANDga(e<TC4011UrJP*l)
6.
2AMJ20H(K4yivUCx
I)
7.
lnvwter(TC4069BPx
I)
S.
Quard Analog Switch Miiltiplover
(TCdOAtBP)
o. ITD(34-di8it
FhMdot LCD)
10.
Key
11. Crystal
(CSB2560)
Brief
overview
of
CPU
I
and
CPU
II
The
CPUs
are
provided with
internal
ROM.
and the
CPUs have
ihe
following assignments
CPU
I
Key
input rostine
Acknowledgement
of
the remaining
program
One
instruction
to
one program
step
additional incoiporatton
Interpreter:
Pio&aiii
execute
italciiuul
CdSSCtlt
tuillfol
MdUlUClil
Cummand
ilateimnt
Pointer
control (leserved)
v
-irii'i
lit
mrinutl
opentnn
Piw.resumt
control
Clouk
Hup
centred
CPU
Display proceHing routine
Input buffer
Cunipuiaiional
result
trr'T
Ai >Uim>tit H'jlirc
Character
geritiatoi
(arctic
routine
Print tontine
Qj,uei
Rprngnitlor: nf printer (reserved)
I'oiver
"t
I
Clojk
nop
• The
CPU
I
iu.ii;;i,
ia
read key-ii data
ur
read
(tie instruction to
be
execute*]
fiom
the
RAM,
and
decides what
is
to be
don*
(or
Iho loiuitl
of aritlunebco':
operation*
(i.e.,
control of arithmetic sequence, memorieingof arithmetical Jots, and
its
-
i I
'
. or interpret the cyntnx
of
the
BASIC instruction for deciding what
is
to be
executed,
or determine* and
prepare*
the information
lo
be
displayed, but
CPU"
I
doei not perfiwm any
execution
By
itself.
Il
only arranges
ihedata and
inlorma-
tlon in
proper sequence
and acts to provide
instruction codelo
the f
PL
II
via the buffer.
On Uteothet hind.
CPU
D
constant-
ly receives
execution
instructions
from
CPU
I
via the transfer buffer
and executes operations
pei
each infraction or ex-
changes
data,
depending on the situation.
Although
it
shares eA«.uiio>! fum-lions
and
tieifoiai*
some
auxiliary
CPU
rolcs.it
does net
perform any
decision
by
itself.
Eg-
Actions of
CPU
I
and t
PU
U at the lime of
key
data entry.
irt
kvv
u
For
ni ui'.
il
operation
of
ihe
Pocket Computet, the uislructlon
code
(key code)
a written
(mo
the
RAM
in the display
chip
(Input buffer) after
Information
is
put through the
kcybwitd and converted into the instruction
code by
CPU
I,
then
this inst-
ruction code (display!
is
transferred
to thoCPt-
1
11
vis the transfer
butler.
As
CPU
D isceivei this
inctmciion.
CPU
II
ther
decodes
this
imtmction
<
display)
and
executes
dlisplay
processing
Upon
the
completion of
this
processing,
it
notitlei
CPU
I,
and
CPU
I
confirms the completion of
the
vak hy
ihe
CPU
11
before lermimtirg
their
function!.