Sharp ER-A450T Service Manual - Page 30

Power supply circuit - error

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2) Power off sequence When the CPU senses a service interruption, it performs the necessary procedures for the CPU to stop. Then the CPU outputs a reset request to the CKDC8. Reset request SHEN DON'T CARE SCK LDRQ RES1 TL 20µsec or more TH 20µsec or more TL+TH

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2) Power off sequence
When the CPU senses a service interruption, it performs the neces-
sary procedures for the CPU to stop. Then the CPU outputs a reset
request to the CKDC8.
Reset request
Fig. 9-3
When the CPU senses a service interruption or an error, it performs
the necessary procedure for the CPU to stop and issues a reset
request.
The CPU procedures necessary for reset request
All CPU interrupts are made DI.
SCK is driven to low.
Keep LDRQ at LOW level for 20usec or more and drive it HIGH.
Loop
to
. During looping, access should not be made to
external memory.
It should be within 140usec from rising of one LDRQ to rising of
another.
When, the CKDC8 senses a service interruption at POF, it stops
displaying. A service interruption procedure is performed after receiv-
ing reset request from the CPU. If the reset request is not sent from
the CPU within 100msec the service interruption procedure is started
after 110
±
10msec to go into the stand-by mode.
Fig. 9-4
3) Key and switch scanning
Fig. 9-5
As the strobe signal, 8 bits of ST0 - 8 are used.
KR0 - KR7 are used as the key return signal. KR10 is used as the
return signal of the paper feed key. KR11 is used as the return signal
of the mode switch.
4) DISPLAY CONTROL
Fig. 9-6
CKDC8 directly drives the LED display unit.
10. Power supply circuit
Fig. 10-1
+24V: Printer, solenoid power
+5V:
VCC (Logic power)
VDD: Battery charge, Battery Back-up power, CKDC-8 Back-up
power
VCH:
Fiscal memory unit (Not in "U" and "A")
20μsec or more
SCK
LDRQ
SHEN
DON'T CARE
TH
20μsec or more
TL
TL+TH
140μsec
<
=
RES1
POF
RES1
110±10msec
356.25μsec
38μsec
KR0~KR7
KR10,KR11
ST0
ST9
CKDC5
G1-G10
SA-SG,DP
LED-display
(for customer)
LED-display
(for operator)
Driver
Power
trans.
DC-DC
Converter
circuit
Battery
circuit
+5V
F1
F2
Switching
regulator
+24V
+
-
~
~
VDD
VCH
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