Service manual

4·1 . Relation of the main CPU·1 to the main
CPU-2
Since two CPUs are linked together, the bus line of ont
CPU is on the sytem bus; the other CPU bus is kept in the
floa ting state.
Shown
in the following table are the bus signals of the two
CP Us in connection.
SC7852 signal name Z.sO signal nama
LH.o803 signal nlml
A15 - AO A15 - AO
A15 - AO
OB7 - DBO 07- DO 07- 00
MREQ
Oppos~rity
of R
MeO
IORC
OPPOS i ~' lty
of
Mel
If!!
If!!
00 ·
WR
WR RIW
• The OD output of the LH -5803 is connected to AD of
t he SC7852 via the gate array ( LR 38041).
The operating
CPU is indicated by the E LH signa l.
ELH '" Lo w: LH -5803
ELH '" High: Z- 80
z.eo Inttnoctlon ~~T38H)A
L H ~ I .. uue_
STA Ir AOlllH. A
Fig. 3
HALT
OUT (38H). A
The following takes place when a reset is applied to the
SC7852
(AsfiN · Lo w ).
<D ELH goes to high to indicate that the Z·80 is in
operation. At the same time, a reset
is app li ed to the
LH-5803.
Thi s allows the Z·80 to operate after the
completion of the
reset_
® Wit h the following instruction, the Z.aO hands down
the control to the LH-5803.
OUT(38H), A .... A is
don't care.
HALT
After the execution
of the abo ve in struction, the Z-80
bus
is set in the floating state. At the same time, £IR
goes to low along with RSTO , and the reset is cleared
to the
LH -5803 to start its operation.
® With the following instructiory, the LH-5803 hands
down the control to
the 2-80,
STA # A038H
A wait is appl ie d to the LH · 580J (L HWA1T "" High) to
stop the operation of the LH ·5803. When E LH goes to
high , the LH -5803 bus is set in the floating state, With
this, the Z·80 starts
to operate.
G) In order that the 2·80 may hand down the control to
the LH -5803. the 2-80 stops after the operation as in
step 2 and the Z-80 bus
is set in tl'le floating state.
- 5 -
Then, t'CH goes to a low leV1!1 so that the LH ·5803 bus
is activated_ LHWAI T now goes to low wh i ch causes
the LH ·5803 to operate.
4-2. Sub CPU role
Th e sub CPU h as the following roles.
(1)
Main power·on and main power·off
<D When the system.off command is received from the
main
CPU, the system is turned off,
® The system is turned on when the system is switched
on
by tl'lelONlkey.
(2) Real timer
<D Similar to the PC -1500; month, day, hours, minutes,
and seconds are controlled
by the PC · l600 , though a
leap year
is not issued.
® A single wake-up timer and two alarm timers (in .
cremented at every 0.5 secon
d) are control led .
(3) Weak battery detection
A weak battery condition
is monitored by the AI D
converter function held by tl'le sub C PU .
<D Thelevel of the PC-1600main power supply is checked.
® Also, the level of the power supply to the PC-1600
option
is c l'l ecked.
When it drops below the given level, the symbo li BATTI
is activated on t l'l e LCD . When the hardware-monitored
weak battery
Signal is turned to h ig h, the system is
tl'len turned off.
(4) Analog input
The
level of the input signal received through the
PC 1600 analog input jack is AI D converted and
returned
to the main CPU .
Also,
an external keyboard input through the same
jack
may be read and returned to the main CPU.
(5) CI ick sound
A click sound feature
is supported by the PC-16(lO.
Wh en a keyboard entry is sensed in the click generate
mode,
tl'le command is issued from the main CPU to
generate a click sound.
(6) Reset sig n al
Two reset Signal input lines are supported. When a
signal
is received on eitl'ler line, a reset is applied to the
system for the prescribed time (30 milliseconds).
CD RESET switch on the back of the PC-1600
® RESET switch on the back of tl'le C E-1 600P
(7) System-on function with the CI s ignal of the RS· 232C
interface
(c hecked at every 0.5 second)
(8) Timer
signa l outp ut (1 /64 sec.)