Oki OKIFAX4550, Maintenance Manual

Page: 278 / 592

41309401TH Rev.4
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2. Explanation of Signal Flow
2.1 OKIFAX4550
(1) Copy Mode
Figure A.4 (1/13) shows the picture signal route in local copy mode
One-line picture data is transferred to A/D converter (analog/digital) via operational amplifier
from the scanning unit (CIS: contact image sensor) as an analog data. After conversion from
analog data to 6-bit digital data by A/D converter, the picture data is sent to IEXSEED (image
processing LSI) and SRAM. Here, the picture data undergoes various kinds of picture
processings (IEXSEED and SRAM), converted to two-level binary data (black and white) and
then sent to IOGA4 (scanning control). The one-line binary picture data from IOGA4 is stored
into DRAM. When the data for one page has been stored in the DRAM, the data is read out from
the DRAM and sent to IOGA4. The data is converted into a serial data by the picture control of
IOGA4 and transferred to the LED print head for printing as HDATA0. Writing of data into the
page memory is also possible during the printing operation.
(2) G3 Send Mode
Figure A.4 (2/13) shows the G3 send picture signal route
In the G3 mode, the data transfer route from the scan unit up to the DRAM is the same as in the
copy mode described in (1).
The picture data for one-line is transferred from DRAM to IOGA4 (CPU). The IOGA4 (CPU)
performs the picture data processing (encode) for this picture data (FILLER, fill bits are inserted
etc.) and again stores into the DRAM. The stored encoded data is output from DRAM to the
MODEM under the control of IOGA4 (CPU). After modulation, the picture signal “S” is sent to
the NCU board as the transmission data. The transmission data “S” goes through the amplifier
and is sent to the telephone line L1 and L2 via the transformer T1 as high speed signal.
(3) G3 Receive Mode
Figure A.4 (3/13) shows the G3 receive picture signal route
In the G3 mode, the high-speed picture signal arriving from the telephone line at L1 and L2 of
NCU passes through the transformer T1 and the amplifier and is input to the MODEM as “R”
signal. After demodulation by modem, the picture data is sent to IOGA4 (CPU). The IOGA4
(CPU) performs the picture data processing (decode) for this picture data and stores into the
DRAM. Then, the stored picture data is again written into DRAM (as a page memory) by the
picture processing control of IOGA4 (CPU). When the data for one page has been stored in the
DRAM, the data is read out from the DRAM and sent to IOGA4. The picture data is converted
into a signal data by the printer control of IOGA4 and transferred to the LED print head for printing
as HDATA 0.
(4) PC Print
Figure A.4 (4/13) shows the signal route in PC Print mode.
The data input from the MCNT's parallel I/F is input, through the IOGA4, to the DRAM using DMA.
The input data is transferred to the Decoding block in the IOGA4 using DMA.
In the Decoding block, the data is expanded in the 1-line raster buffer in the IOGA4. Then, the
expanded data is sent to the video block in the IOGA4 in response to a 1-line synchronous signal.
In the video block, image processing is performed for printing and the resultant data is
transferred to the LED head.
(5) PC Scanner
Figure A.4 (5/13) shows the signal route in PC Scanner mode.
The data transfer route from the scan unit up to the DRAM is the same as in the copy mode
described in (1).
The data input to the IOGA4 is temporarily written into the external DRAM (4 megawords x 16
bits). The written data is compressed to TIF data by firmware, then written into the external
DRAM again.
The written TIF data is sent to the MCNT's parallel I/F through the IOGA4.