Lexmark W820 Service Manual page 35

Printer Control Components
The printer control is made up of the MCU PWB, the I/O PWB, and numerous connected
components.
Machine Control Unit PWB (MCU PWB)
The printer receives status and command information from the I/O PWB and from the
ESS PWB and controls most printer operations. The MCU PWB performs nine major
functions:
1.
Communicates with the Printer Controller (ESS).
2.
Maintains the system clock.
3.
Controls the printing process.
4.
Controls the Printhead, the Fuser, and the drive assemblies.
5.
Distributes +5VDC and +24VDC to various printer components.
6.
Monitors printer status.
7.
Maintains a running print count.
8.
Maintains NVRAM settings.
9.
Controls printer options.
The ESS PWB is connected to the MCU PWB. Video data travels from the ESS PWB,
through the MCU PWB to the Laser Diode PWB.
4025-XXX
1-17
General Information