2HJ/2HK
2-1-16
Data to print is processed by the main controller PWB and transferred to the LED print head relay PWB in synchronization
with VIDEO signal through the engine controller PWB. VIDEO signal is sent from ASIC (U22) on the mail controller PWB
to ASIC (U1) on the LED print head relay PWB using LVDS method. LVDS stands for Low Voltage Differential Signaling
which uses 16 pairs of signal lines (32 in all).The main controller PWB converts VIDEO signal into a unique format using
LVDS depending on compensating data stored in a flash memory.
The LED print head has an EEPROM on the LPH PWB. The EEPROM includes data for compensating the fluctuation of
luminosity of every LED chip. At power-up, the compensating data in EEPROM are cached in the flash memory on the
main controller PWB. In a subsequent power-up, the main controller PWB refers the flash memory to obtain the compen-
sating data and the EEPROM is checked with its checksum only.
If the LED print head or the main controller PWB is replaced, checksum becomes error. The compensating data is trans-
ferred to the main controller PWB again from the EEPROM. In case of failure with EEPROM on the LPH PWB or with com-
pensating data, the printer displays service call 0951, 0952, 0953, or 0954 within approximately 30 seconds.
Figure 2-1-20LED print head block diagram
Drum
LVDS
LVDSP0 to 11
LVDSN0 to 11
Microcontroller
(U8)
LVDS: Low Voltage Differential Signaling
ADATA 10 to 19
ADATA 20 to 29
ACLK, ASCLK
AHSYNC, ASTBN
LED print heads
relay PWB
Engine
controller
PWB
Main
controller
PWB
Drum unit
LED
print head
LPH PWB
EEP
ROM
Serial
communication
Serial
communication
Flash
memory
VIDEO
data
output
ASIC
(U22)
ASIC
(U1)
EEDATA
SOUT
SIN
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