PC-1600
CD
After the system reset has been cleared, the Z-80 starts
operation within 10 microseconds and the Z-80 begins
to read the contents of the address OOOOH.(MREQ
issued)
® Now, the Z-80 starts to supply cloek pulse to the
HD61203 LCD driver (217KHz on the CKO) to
activate the LCD.
• The LCD voltage VEE is activated at the same time
the system is turned on.
• Supply voltage VDO on the RS·232C high level side
will be issued only when PRIM is at a high state.
But, VOD is not supplied during power-on because
PRIM is at a low level then.
• A high ELH state indicates that the Z-80 is started
at the time of system reset. The LH-5803 stays
reset (RSTO;High).
7-3. Reset operation
7-3-1. Reset by the ALL RESET switch on the back of the
PC-1600
When the ALL RESET switch is pressed, it causes the
subcontroller Input ACL to go high. With this, the sub-
controller takes the following action by means of the
hardware.
(1) All input and outpur lines, including P3 ~ PO, are
set in the Input mode.
PI
=
SLCB
PO
=
RSTIN
RESETSW
ACL-50347C
ACL·LU57BI3P
__..:,P3 .....,PO ~ The same state as system-on
In the input mode
(80 microseconds)
CD
Regardless whether the system is turned on or off,
P3~PO are set in the input mode and are kept in the
floating condition while the reset is applied to the
subcontroller.
P3 is pulled up with the resistor.
P2 is pulled down with the resistor.
Pl is pulled up with the resistor.
PO is pulled down with the resistor.
While P2~PO are pulled down towards the non-actlve
direction, P3 is pulled up towards the system-off. So,
the system's power supply is turned off in those states.
However, the power is supplied to the svstorn while the
RESET switch is in depression.
7-3-2. Reset by the RESET switch on the back of the
CE-1600P
When the RESET switch on the back of the CE-1600P
is pressed, KL and Z15 of the subcontroller go high. When
this pulse width continues for more than 300 micro-
seconds, the subcontroller proceeds in the same way as
the system power-on procedure so that areset is applied
to the system.
7-3-3. Difference from ALL RESET
The subcontroller interrogates the s'tate of the BREAK/ON
key at 7-3-1 and 7-3·2 above in the following manner.
(1) If the BREAK/ON key is depressed, the all reset is
assumed and all internals are intialized.
(2) If the BREAK/ON key is not depressed, the reset is
assumed - the procedure to turn the system on from
the system-off state. The internals are not initialized
in this case.
It is possible to return reset from all reset by arequest
from the main CPU, the Z-80 asks the subcontroller
for the cause when the reset is applied. Processing
differs depending on the cause.
In the case of all reset ... Clears all memory contents.
In the case of reset ... Retains all memory contents.
7-4. LCD block
7-4-1. General
The LCD is 1/64 duty and consists of 156 x 32 dots and
has 16 symbols.
Y64 (IC3)
Xl-X32
Yl-Y64 (IC3)
(IV)
X49-X64
(11)
(1111
(I)
X33-X64
Yl-Y64
Yl-Y28
Yl-Y64 (IC2)
The 32 vertical dots comprise the following:
(1) Xl~X32 of the IC2 LCD driver outputs take care of
64 dots from the left.
(2) Xl~X32 of the IC3 LCD driver outputs take care of
65~128 dots.
(3) X33"'X64 of the IC2 LCD driver outputs take care of
129~156 dots in conjunction with Yl ~Y28.
(4) X49~X64 take care of 16 symbol dots in conjunction
with IC3 Y64.
7-4-2. Operation
(1) The LCD driving basic clock (217KHz) supplied from
CKO of the SC7852 is connected to the LCD common
driver. Without this signal, the LCD will burn out when
a DC voltage is applied to the LCD.
This signal is issued only during the system-on time
which appears immediately after the clearing of the
reset. As it is in a low state during the reset, a DC
voltage is added to the LCO during that period.
-12-
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