Canon BJ-W3000 Service Manual page 65

CHAPTER 2. BASIC OPERATION
Major functions of the ICs on the image
controller are as follows.
[1] Serial controller (U632)
Uses the external clock of 14.7MHz
divided by 2.
Baud rates for receiving image data over
the serial interface are 2400, 4800, 9600,
19200, and 38400bps.
[2] FIFO (U622)
This buffer stores the image data tempo-
rarily between the parallel interface and
CPU (U607).
[3] DRAM (U602, U606, U611, U616)
4 RAM chips with a capacity of 2
Mbytes each, connected to the gate array
using a 32-bit data bus, and used as
follows.
• Storage area for the CMYK bitmap
data created by the CPU (U607) for the
banding process.
• CPU system processing work area.
[4] SRAM (U628)
32 Kbyte memory used to store the raster
slice converted image data until a trans-
mission request is received from the
engine controller.
2–8
[5] Timer (U610)
Uses the by external clock of 14.7MHz
divided by 2.
Functions as a baud rate clock for the
serial controllers. (U632, U633)
[6] Serial controller (U633)
Uses the external clock of 14.7MHz
divided by 2.
Intermediary between the gate array
(U617) and engine controller.
[7] Gate array (U617)
Major functions are as follows.
• DRAM control
• Raster slice conversion of the image
data in the DRAM after banding
processing, to slice data to the width of
the BJ cartridge
• Address decode
• 8-bit parallel output of image data
to the engine controller
• Controls the compatible and nibble
mode latch timing for image data
transfer from the computer.