Sharp FO-475TH, UX-258TH manual Circuit description

UX-258TH

FO-475TH

CHAPTER 5. CIRCUIT DESCRIPTION

[1] Circuit description

1. General description

The compact design of the control PWB is obtained by using ROCK- WELL fax engine 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

TEL/LIU

PWB

CONTROL

PWB

LCD

PWB

POWER

SUPPLY

PWB

PANEL

3. Operational description

Operational descriptions are given below:

•	Transmission operation
	When a document is loaded in standby mode, the state of the docu-
	ment sensor is sensed via the 1 chip fax engine (FC200). If the sen-
	sor signal was on, the motor is started to bring the document 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 con-verted 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 FC200 controls the procedure signals from the modem to
	be ready to receive data. When the program goes into phase C, the

PWB

AC CORD

serial data from the modem is converted to parallel form in the mo-

dem interface of the 1 chip fax engine (FC200) which is stored in the

TX/RX

MOTOR

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 (R96V24) which is installed on the control PWB.

2) TEL/LIU PWB

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

3) Power supply PWB

This PWB provides voltages of +5V and +24V to the other PWBs.

4) Panel PWB

The panel PWB allows input of the operation keys.

5) LCD PWB

This PWB controls the LCD display.

receive 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

FC200 which is then converted from parallel to serial form to be sent

to the thermal head. The data is printed line by line by the FC200

which is assigned to control the motor rotation and strobe signal.

• 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 1

chip fax engine (FC200) which is then sent to the image buffer of the

RAM. Next, the data is transferred to the recording processor in the

DMA mode to send the image data to the thermal head which is

printed line by line. The copying takes place as the operation is re-

peated.

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