Sharp A260 Service Manual - Page 29
Circuit Description
UPC - 074000033733
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CHAPTER 5. CIRCUIT DESCRIPTION [1] Circuit description 1. General description The compact design of the control PWB is obtained by using CONEXANT fax engine in the main control section and high density printing of surface mounting parts. Each PWB is independent according to its function as shown in Fig. 1. 2. PWB configuration MOTOR CIS LCD PWB PANEL PWB CONTROL PWB TEL/LIU PWB POWER SUPPLY PWB AC CORD Fig. 1 1) Control PWB The control PWB controls peripheral PWBs, mechanical parts, transmission, and performs overall control of the unit. This machine employs a 1-chip modem (SCE214V) 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. UX-A260U 3. Operational description Operational descriptions are given below: • Transmission operation When a document is loaded in stand-by mode, the state of the document sensor is sensed via the 1 chip fax engine (SCE214V). 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 image 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 automatic receive mode. First, the SCE214V 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 chip fax engine (SCE214V) which is stored in the 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 SCE214V 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 SCE214V 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 (SCE214V) 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 repeated. justmanuals.com 5 - 1