Epson LQ-570 Service Manual page 25

REV.-A
2.3.4 MOTOR, CR Drive
Figure 2-22 shows the MOTOR, CR driie circuit. An open-loop, constant-current drive control is used
to drive the MOTOR, CR. The motor is driven by 2-2 phase excitation and 1-2 phase excitation. 2-2
phase excitation corresponds to two 1-2 phase excitation steps. Thus, for each single step phase
change of a 2-2 phase excitation motor, the carriage moves 1/120 inch. For each single step phase
change of a 1-2 phase excitation motor, the carriage moves 1/240 inch.
The MOTOR, CR driie circuit of the STK-67128 detects the amount of current flow in the MOTOR, CR
coil and regulates it. The current flowing through the coil varies depending on the speed of the
MOTOR, CR.
The amount of current is set by the CPU via the E05A50 l/O port. Signals are sent to Vrefl or Vref2
on the STK-67128. The STK-67128 sets the coil current to mnespond to the MOTOR, CR speed.
Ports P60 to P63 on the CPU are used exclusively as phase control potts for the stepping motor.
-
Drive Mode
Extension Type
3 x speed 2-2 phase
2 x speed
2-2 phase
1.5 x speed
2-2 phase
4/3 x speed
1-2 phase
1 x speed
1-2 phase
3/4 x speed
1-2 phase
2/3 x speed
1-2 phase
1/2 x speed
1-2 phase
Circuit
Current
Control
Circuit
Figure 2-22. MOTOR, CR Drive Circuit
Type Drive Frequency
2695
1773 pps
1347 pps
1191 pps
1796
1347 pps
1190 pps
898
2-17
Al
/Ad
Standard Print Character
Draft
High Speed LQ
LQ