Epson DFX-5000+, Service Manual

Page: 90 / 223

Operating Principles
PF Motor Driver Circuit
Stepping motor driver SLA7026 drives the PF motor. Figure 2-27 shows
the PF motor driver circuit block diagram, and Table 2-6 provides the PF motor
specifications
PFI I-
PFA
-A PFB
B PFC
INB -B PFD
Figure 2-27. PF Motor Driver Circuit
The motor pulse switching signals are transmitted from CPU ports PGOO to PG03.
The PF motor is controlled using open-loop phase switching based on the specified
time data, and the phase driving method is l-2 phase excitation. (When the PF
motor is held, the phase driving method is 2 phase excitation.) The CPU selects
the most suitable driving mode from the modes below according to conditions
such as the paper feed step number and the pull tractor condition.
Micro feed (adjust) mode
Normal speed mode
Middle speed mode
Each phase switching FET in driver is an open collector. When the phase
switching data is HIGH, the motor is turned on. The PFA port gate array
monitors the phase A signal PF motor and checks whether it is operating
normally. The PFA port is used as the WDT (watch dog timer). If PF motor
operation is abnormal, the gate array outputs the RSTOUT (reset request) signal
to the CPU and the
V system reset IC (IC9).
2-38
EPSON Service Manual