Toshiba ESTUDIO170F, Service Manual

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7
January 2005 © TOSHIBA TEC e-STUDIO170F Circuit Description
7 - 27
7.3.3 LSU Drive Circuit
Fig.7-21
The LSU (Laser Scanner Unit) drive circuit consists of the Engine-CPU (IC37), ASIC (Engine controller:
IC15) and other peripheral devices. It drives the LSU connected to CN3 and CN8 on the Main PBA to
apply a laser beam to the drum.
The ASIC sends a printing command to the Engine-CPU by the CMD signal. This allows the Engine-
CPU to drive the polygonal motor in the LSU to make the polygonal mirror rotate. When the printing is
ready, the Engine-CPU sends a TOD signal and a UFEX signal to the ASIC.
The ASIC reads the raster data accumulated in the SDRAM (IC1) and serially converts them to a
LDATA signal. Then the ASIC detects the clock signal (OSC1 or OSC2) outputted from the facsimile
oscillator (X1) or the printer oscillator (X2) according to the timing of the TOD signal and the UFEX sig-
nal, and sends the LDATA signal to the LSU according to the timing of the clock signal.
The LSU radiates a laser beam according to the input LDATA signal to make a latent image latent on
the drum.
Signal Name Type Active Description Destination
CMD O - Serial communication command signal Engine-CPU
TOD I L Top of data signal Engine-CPU
UFEX I L Horizontal synchronizing signal Engine-CPU
LDATA O - Print data IC14
PTCCK1 I - 16 dots/mm clock X1
PTCCK2 I - 300/600 dpi clock X2
LSU
230
231
34
40
19
8
9
10
2
3
1 2
25, 26
25
33
236
235
234
SDD0-15
Control signal
Control signal
IC14
IC14
CN3
CN8
PTCCK1
PTCCK2
CMD
LDATA
UFEX
TOD
Main PBA
X1
41.716
MHz
X2
47.234
MHz
IC15
ASIC
(Engine controller)
IC37
Engine-CPU
IC1
SDRAM