Epson FX-980 - Impact Printer, Service Manual

Page: 35 / 72

FX-980 Revision A
Operating Principles Control Circuit 35
2.3.5 PF Motor Driver Circuit
The figure below shows the PF motor driver circuit.
Figure 2-7. PF Motor Driver Circuit
IC 12 driver receives phase data from the CPU and gate array. The PF
driver current is controlled by the 74LS32 using port 61 (P27) of IC2.
These controlled drive currents are output to ports 2 (I10), 1 (I11), 23
(I20), and 24 (I21) of the A2917SEB.
2.3.6 EEPROM Control Circuit
The EEPROM is nonvolatile memory that stores information even if the
printer power is off. The figure below shows the EEPROM control
circuit.
Figure 2-8. EEPROM Control Circuit
The EEPROM is controlled by CPU ports 9 (P70), 10 (P71), 11 (P72),
and 12 (P73). Port 11 is the data output line used to save the
information to the EEPROM, and port 12 is the data input line used to
read the saved data from the EEPROM. Port 70 is the chip select line,
and port 71 is the clock timing line. When the PWDN signal (power
down) is detected on port 20 (INTO), the CPU writes the necessary data
to the EEPROM before the +5 V line drops to 4.75 V.
2
1 I 1 0
I 1 1
2 3
2 4 I 2 0
I 2 1
6 1
P 2 7
I C 2 C P U
6 8 P F I 1
I C 1 G . A .
6 7 P F I 2
I C 1 2 A 2 9 1 7 S E B
I C 1 1 7 4 L S 3 2
6
3
1 8
2 1
C N 1 0
1
3
2
4
A
/ A
B
/ B
PH
1 PH
2
43 26
P P 6 0 1 0
9
P P 6 1
P G 1 0
5
P G 1 1
6
C P U
P 7 0
P 7 1
P 7 2
P 7 3
C S
D I
D O
E E P R O M
9
1 0
1 1
1 2
1
2
3
4 I C 8
I C 2
S K