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b. RESET generation circuit
The RESET signal is formed by the power voltage detection signal
(POFA) and the data transfer complete signal (DCH) from the
CPU. It is used to operate the circuits in the DC power voltage
stable area.
The RESET signal is set (the operation enable state) when the
POFA becomes HIGH (+5V). It is reset (the operation stop state)
when the DCH becomes LOW (0V).
Besides, when the POFA becomes LOW, data are transmitted
from the CPU to the EEPROM. After completion of data transmis-
sion, the DCH becomes LOW.
ON
POWER
VB
VB
VC
VD2
V D
0V
FW
POFA
RESET
207.03ms
DCH
CPU,R OM,I/O and EEPR OM
Operation start
c. Operation at power ON
•
Immediately after power ON, the FW rises to turn on the collec-
tor and the emitter of Q210.
Since the IC206 4pin voltage becomes about 0.736V, which is
lower than the 5pin voltage (ZD103: 5.2 ∼ 5.5V), and 2pin is
open.
•
The 24V rises after about 16msec from rising of the FW and
C110 is charged through R287 and D212. In about 95msec,
the IC206 7pin voltage becomes higher than the IC206 5pin
(ZD103: 5.2 ∼ 5.5V) and 1pin becomes HIGH.
•
The IC206 1pin becomes HIGH to turn on the collector and the
emitter of Q211. The Q211 collector becomes LOW to turn off
Q213. The POFA is driven HIGH through R294.
d. Operations at power OFF
•
Immediately after power OFF, the FW rises to open the collec-
tor and the emitter of Q210, and C111 is charged through
R276. In about 30msec, the IC206 4pin voltage becomes
higher than 5pin (ZD103: 5.2 ∼ 5.5V) to drive 2pin LOW.
•
The 24V starts rising about 16msec behind from FW. IC110 is
charged through R287 and D212. The IC206 7pin voltage be-
comes higher than the reference voltage of the IC206 5pin
(ZD103: 5.2 ∼ 5.5V), and the 1pin voltage becomes HIGH.
•
The IC206 1pin becomes LOW to turn off Q211. The High level
is inputted to Q213 through R291 to turn on and to drive the
POFA LOW.
OFF
20ms
19V
(38ms)
30ms
<30ms
Circuit
Data transfer between
operation stop
CPU/EEPROM
e. Operations at instantaneous service interruption
Since the POFA signal is outputted from IC206, the POFA signal
may be erroneously delivered due to the difference in rising time
of 5V and 12V power. Therefore the power voltages of 5V and
12V are monitored by IC206 to control the POFA signal.
•
When the power is turned OFF, the POFA signal must be
driven LOW (0V) in an early stage. If, however, it is driven low
too early, the machine will stop at an instantaneous service
interruption (30msec or less) which does not affect the machine
operations. Therefore in this circuit, if the AC power is turned
off continuously for more than 30msec, it is judged as power
OFF and the POFA is driven LOW.
•
In normal operation, the IC206 4pin voltage is LOW. In an
instantaneous service interruption, the FW becomes LOW im-
mediately to open the collector and the emitter of Q210, charg-
ing C111 through R276. It takes 30msec for the IC206 4pin
voltage to rise above the reference voltage (IC206 5pin 5.2 ∼
5.5V). In an instantaneous service interruption below 30msec,
the machine will not stop.
f. Operations when the power voltage falls
•
When the AC power voltage falls below the specified level, the
DC power voltage falls though the DC power circuit is the
regulator circuit.
Then the 24V voltage is detected, and when it falls below 19V,
the POFA is driven LOW (0V). (When it falls below 19V, the
IC206 5pin voltage is divided by R287 and R288 to be lower
than the reference voltage of 9pin. Therefore the comparator
(IC206) output becomes LOW.)
9 – 13
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