Sharp SF-2052 Serviceanleitung Seite 228

[b] Reset circuit
This circuit generates reset signals for the CPU and the external G/A, and is composed of IC6 and its peripheral circuits.
IC6 is provided with the reset function activated when the power is turned on and when the power falls below +5V.
The reset state is maintained until a certain time passes from when the power voltage reaches about 4.3V after supplying the power. The reset
maintaining time depends on the capacity of C9.
This circuit is also provided with the watch-dog timer function.
The watch-dog timer is built in the G/A (IC7) It starts the operation (count down) when RES2 turns HIGH. When RES2 is driven LOW, the watch-dog
timer count value is reset to the initial value. It monitors hung-up or other abnormalities of the CPU.
For monitoring, data (initial values) are written from the CPU to the G/A once for every 5ms. (Resetting to the initial values every 5ms.) The data are
counted down inside the G/A. Since the values are reset to the initial values every 5ms, the count normally does not fall to zero. If, however, a
hung-up of the CPU occurs, the data are not reset to the initial values, and the counter becomes zero. At that time, a H signal is inputted to NMi pin
of the CPU from G/A, and reset is performed by the software, and retry is performed until the CPU is resumed.
To main body via
interface cable
[c] Paper feed motor (DFM) drive circuit
This circuit controls the paper feed motor rotation and stop and the rotating direction. It is composed of the G/A (IC7) and the exclusive hybrid IC
(IC10), etc.
The motor rotation, stop, and rotating direction are controlled by the combination of binary logics inputted to the G/A through the data bus from the
CPU.
This provides control signals to the G/A 65 ∼ 68 pins.
The G/A 65 pin and 66 pin are for the PWM output for speed control. (Normal rotation, 65 pin; reverse rotation, 66 pin)
These signals are inputted to IC10.
IC 10 is a hybrid IC including 4 power MOSFET's, and drives the motor by taking the G/A output 65 ∼ 68 pins.
The motor operates as follows by the combination of 65 ∼ 68 pins.
— 65
Before start 0
CCW 0
CW PWM
Brake 0
In the brake mode, the both terminals of the motor are shorted, generating a great braking torque to stop the motor.
G/A
(IC7)
MIH1
MIL1
MIH2
MIL2
CHGCLK
+5V
R61
4.7K
DF3-6P-2DSA
6
RESET
CN9-6
66 67 68
0 0 0
PWM 1 0
0 0 1
0 1 1
14
67
INA
12
65
INB
68 15
INC
3
66
IND
72 1
CLK
+5V
13
VCC2
16
SG
C49
0.1µ F
To power control circuit
Paper feed motor drive circuit
R58
4.7K
D6
R52
4.7K
DSA010
C43
R30
0.1µ F
10K
+5V
+5V
7
IC6
VCC
5 6
C4
C OUT
GND
1000PF
4
C9 M51953BFP
0.33µ F
Reset circuit
IC10
10
OUT1-1
L1 72µ H
1
11
OUT1-2
SK-8MS-5W
6
OUT2-1
L2 72µ H
2
7
OUT2-2
SK-8MS-5W
2
FD+24V
VZ
9
C34
VCC1-1
8
1µ F
VCC1-2
C28
0.1µ F
STK681-050
PGND
12 – 25
+5V
TP18
Q5
2SC2712
+5V
TP23
R5 R9
IC5.3
22K 10K
6 5
NC
HD74LS06FP
DF1B-9P-2^5DSA
DFW1 CN5-1
DFM
DFW2 CN5-2
CPU
NMI
CPU
(IC11)
7
*RESET
C44
0.1µ F
G/A
(IC7)
37
RES1
C42
0.1µ F
38
WDT
39
RES2
Paper feed
motor