Reset Circuit; Motor Driver Circuit - Epson Stylus PHOTO 1270 Service Manual

EPSON Stylus Photo 870/1270

2.2.2.2 Reset Circuit

Reset circuits are attached on the C304MAIN board to monitor the two
voltages: +5V for the logic line and +42V for the drive line. When each
circuit detects abnormality on the corresponding line, it resets CPU and
ASIC to prevent the printer from operating abnormally. IC5 RTC-9820SA,
the reset circuit IC attached directly on the main board, monitors both +5V
and +45 lines but can reset them independently. See Figure 2-14 for the
block diagram for the reset circuits.
+42V
+5V
D2
SB007-03CPTB
C18 C19 C21
0.1U 0.1U 0.1U
BAT1
CR2032
Figure 2-14. Reset Circuit Block Diagram
"
+5V line reset circuit
The VDD port of IC5 reset IC monitors the +5V line. When the IC
detects an abnormal voltage level (4.3 V or lower), it outputs a reset
signal from the RST port to CPU and ASIC.
"
+42V line reset circuit
The VIN port of the IC5 reset IC monitors the +45V line. When the IC
detects an abnormal voltage level (35.5V or lower), it outputs a reset
signal from the VDT port to CPU and ASIC.
NOTE: IC5, also serving as RIC (Real Time Clock), manages timer control
when the printer power is turned off. Power for this operation is
supplied from the BAT1.
OPERATING PRINCIPLES
+3.3V
IC8
R27 E05B70CD
3.3K
R26
3.3K
VDT NMI
VIN
VDD
MRES
FRST
RST RESET
VBK TCE
CE
TCLK
SCLK
TDATA
DATA
GND
Electrical Circuit Operating Principles

2.2.2.3 Motor Driver Circuit

The Stylus Photo 870/1270 is equipped with the CR motor and PF motor
that are DC motors and ASF/Pump motor, a stepping motor. To control
the DC motors, a slave CPU is mounted on the C304MAIN board beside
the CPU and ASIC. Since the slave CPU is exclusively used to control DC
motors, it reduces duty of CPU and ASIC to offer faster data processing.
CR motor driver circuit
The internal equivalent circuit of the CR motor driver IC (LB1947) is as
shown below.
IC8
IC15
E05B70CD
C90A13CA
ENA
NMI
CRAI0
CN8 NMI
HEAD FFC
CRAI1
RXD1
P31
ENB
TXD1 P33
CRBI3 P32
CRPHAB P30
CRENBB P64
CRAI2 RES
MD2
P12
P11
P13
CRBI2
P27
P26
CRBI3
CPU
P25
Figure 2-15. Internal Equivalent Circuit of the CR Motor Driver IC
The Slave CPU (C90A26CA) controls the CR position by referring to the
pulses sent from the linear encoder via ASIC (IC18). Based on the data
sent from ASIC, the CPU sets an appropriate drive current value used to
Revision B
+42V
+5V
IC18
LB1947
C115
0.1U
VBB
OUTA CR-A
PE1 IN1
CR-B
OUTB
PE2 IN2
ST
PE0
R115
PE4
VI
68BK
CR
MD
PA0
C117
R114
1500p
12.7K
R112
0.499
E
VREF
DA1
GND
-
R138
IC24 +
4.4BK
M62552FP
R139
4.99BK
49