Mbu - Ricoh B121 Service Manual

DRAM
• The 8 MB of DRAM is shared as follows.
SAF memory
Working memory : 3 MB
Page memory
Memory back-up
• A rechargeable battery backs up the SAF memory (DRAM) for 1 hour.

4.2.2 MBU

On this board, the flash ROM contains the FCU firmware, and the SRAM contains
the system data and user parameters. Even if the FCU is changed, the system
data and user parameters are kept on the MBU board.
ROM
• 3MB flash ROMs for system software storage
2MB (16bit x 1MB) + 1MB (16bit x 512K)
SRAM
• The 128 KB SRAM for system and user parameter storage is backed up by a
lithium battery.
Memory back-up
• A lithium battery backs up the system parameters and programmed items in
the SRAM, in case the base copier's main switch is turned off.
Switches
Item
CN1 Switches the SRAM backup battery on/off.
SM
: 2 MB
: 1.5 MB
Description
75
BOARDS
B620