Service manual

2.3.2.3 Carriage Motor Driver Circuit
Carriage motor driver IC SLA7043 (IC15) outputs a constant current to drive the carriage motor in the printer
mechanism. Gate array E05B21 (IC2) decides the motor phase and speed, and then it sends a signal to the
carriage motor driver IC (SLA7043), using the 4-bit serial transmission line. The first bit indicates the
direction of motor rotation. The other three bits (a, b, c) are current duty data for the motor speed for each
printing sequence. (Refer to Table 2-2, below.)
SLA7043 can select the reference voltage itself based on these three bits of current duty data. Also, the driver
IC receives these signals via two serial transmission lines for the two motor phases (phase A and phase B). As
a result, the carriage motor can be driven in micro step sequence (
1
⁄
720
inches, minimum). The SLA7043
motor driver reads four-bit serial data using four clock counts from the E05B21 (IC2) clock.
Each bit is read at the falling edge of the clock pulses. Then, received serial data is written into the shift
register and then shifted the latch register. When the strobe pulse becomes active from the E05B21 (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 2-2. Serial Data Contents
Mode c b a* Vref (Typical)
0 000
Vref × 1/3
(Vref = +5 V)
× 0%
1 001
×20%
2 010
×40 %
3 011
×55.5%
4 100
×71.4%
5 101
×83%
6 110
×91%
7 111
×100%
* “a” indicates the 2nd bit, “b” indicates the 3rd bit, and “c” indicates the 4th bit.
The following figure shows 4-bit serial data and how this data is transferred by the SLA7043 driver. The step
time for the reference voltage is determined by the interval time of the strobe pulse.
E05B21
(IC2)
199
196
198
197
CRBSO
CRSTB
CLKA
5
16
2
13
CRASO
SLA7043
(IC15)
CLKB
STBA
STBB
DATA A
DATA B
6
17
CRV0-5
REF A
REF B
CRHOLD
RSA
RSB
3
14
9
10
CRCLK
B
E
C
A
A
B
B
1
8
11
18
1
2
3
4
+
3
5
V
5
(CN6)
5-10
205
GND
Q5
Figure 2-4. Carriage Motor Circuit Block Diagram
Stylus Pro XL+ Service Manual Operating Principles
Rev.A 2-5