Epson Stylus pro 7700m, Service Manual

Page: 46 / 139

2.3.2.3 Carriage Motor Drive Circuit
The carriage motor drive IC SLA7041MS (IC15) outputs a constant current to drive the carriage motor for the
printer mechanism. Gate array E05B09 (IC2) decides the motor phase and speed and then sends a signal to the
carriage motor driver IC (SLA7041MS) using the 4-bit serial transmission line.
The first bit indicates the direction of motor rotation. The other three bits are current duty data for the motor
speed of each printing sequence. SLA7041MS can select the reference voltage itself based on these three
current duty data bits. Also, it receives these signals by two serial transmission lines for the two motor phases
(phase A and phase B). Due to this, the carriage motor can drive micro step sequence (
1
⁄
720
inches, minimum).
The SLA7041MS motor driver reads four-bit serial data using four clock counts from the E05B06 (IC2)
clock. Each bit is read at the falling edges of these clock pulses. As a result of this, received serial data is set
into the shift register and then shifts the latch register. When the strobe pulse becomes active from the E05B06
(IC2), serial data is moved into the reference voltage selection circuit and the voltage is changed. Therefore,
when the printer is in the constant speed mode, this strobe pulse becomes inactive. The following table
indicates the current duty of each carriage motor speed mode.
Table 2-8. Serial Data Contents
Mode c b a Vref (typical)
0 0 0 0
Vref
×
1/3
(Vref = +5V)
×
0%
1 0 0 1
×
20%
2 0 1 0
×
40 %
3 0 1 1
×
55.5%
4 1 0 0
×
71.4%
5 1 0 1
×
83%
6 1 1 0
×
91%
7 1 1 1
×
100%
NPN Tr
(Q27, 2 8)
E05B09
(IC2)
2 5
2 9
2 8
CR B
CRSTB
C L K A
5
1 6
2
1 3
CR A
SLA7041MS
(IC15)
C L K B
S T BA
S T BB
DATA A
DATA B
6
1 7
C RV RF REF A
REF B
CRHLD
(PA6)
R S A
R S B
3
1 4
9
1 0
CRCLK
(PB0-PB7)
B E
C C
A
A
B
B
1
8
1 1
1 8
1
2
3
4
+35V
5
(CN6)
3 0
31-38
5 6
Figure 2-20. Carriage Motor Circuit Block Diagram
Operating Principles Stylus Pro Service Manual
2-16 Rev.A