Sharp FO-2970M Service Manual Download

Page: 37 / 114

FO-2970MU

CHAPTER 5. CIRCUIT DESCRIPTION

[1] Circuit description

1. General description

The compact design of the control PWB is obtained by using Risc Proc-
essor (CPU) in the main control section and high density printing of
surface mounting parts. Each PWB is independent according to its func-
tion as shown in Fig. 1.

2. PWB configuration

Fig. 1

(1) Control PWB

The control PWB controls peripheral PWBs, mechanical parts, trans-
mission, and performs overall control of the unit.
This machine employs a 1-chip modem (FM336) which is installed on
the control PWB.

(2) TEL/LIU and Hook SW PWB

This PWB controls connection of the telephone line to the unit.

(3) Power supply PWB

This PWB provides voltages of +5V, VREG and +24V to the another
PWB.

(4) Panel PWB

The panel PWB allows input of the operation keys.

(5) Printer PWB

This PWB controls the printer mechanical parts.
This PWB employs 8 bit CPU that is installed on printer PWB.
This CPU control a printer mechanical parts.

(6) LCD PWB

This PWB controls the LCD display.

3. Operational description

Operational descriptions are given below:

•

Transmission operation

When a document is loaded in stand-by mode, the state of the docu-
ment sensor is sensed via the ASIC (IC15).
If the sensor signal was on, the motor is started to bring the docu-
ment into the standby position. With depression of the START key in
the off-hook state, transmission takes place.

Then, the procedure is sent out from the modem and the motor is
rotated to move the document down to the scan line. In the scan
processor, the signal scanned by the CIS is sent to the internal im-
age processor and the AD converter to convert the analog signal into
binary data. This binary data is transferred from the scan processor
to the image buffer within the RAM and encoded and stored in the
transmit buffer of the RAM. The data is then converted from parallel
to serial form by the modem where the serial data is modulated and
sent onto the line.

•

Receive operation

There are two ways of starting reception, manual and automatic.
Depression of the START key in the off-hook mode in the case of
manual receive mode, or CI signal detection by the LIU in the auto-
matic receive mode.

First, the CPU(SH2) controls the procedure signals from the modem
to be ready to receive data. When the program goes into phase C,
the serial data from the modem is converted to parallel form in the
modem interface of the 1 fax CPU(SH2) which is stored in the re-
ceive buffer of the RAM. The data in the receive buffer is decoded
software-wise to reproduce it as binary image data in the image buffer.
The data is DMA transferred to the recording processor within the
ASIC (IC15) and sent to the LSU on printer PWB.
CPU (SH2) and ASIC (IC15) control printing data, LSU, main motor,
high-voltage circuit, heater control and fan motor.

•

Copy operation

To make a copy on this facsimile, the COPY key is pressed when the
machine is in stand-by with a document on the document table and
the telephone set is in the on-hook state.

First, depression of the COPY key advances the document to the
scan line. Similar to the transmitting operation, the image signal from
the CIS is converted to a binary signal in the DMA mode via the
reading processor which is then sent to the image buffer of the RAM.
Next, the data is transferred to the ASIC in the DMA mode to send
the image data to the printer PWB in order to print. The copying takes
place as the operation is repeated.

LINE CABLE

HEATER

LAMP

AC CORD

OPERATION
PANEL PWB

CIS

LCD

MOTOR

FAN

MOTOR

LSU UNIT

PICK UP SOLENOID