Specifications

2–12
Principles of Operation
Common Controller Board (CCB)
The Common Controller Board (CCB) oversees and coordinates all printer
functions. It is functionally two units: the data processing unit (DPU) and the
real–time processing unit (RTPU). The DPU converts all character data into
printable dot images. The DPU is the high–level logical controller of the
printer; it is not involved in real–time or hardware–dependent printer
operation. The RTPU operates the host interfaces, operator control panel, and
the print mechanism. The RTPU also monitors the fault circuitry in the
mechanism.
The DPU and RTPU communicate by means of shared memory. The DPU
gets host and operator input from buffers in shared memory which are filled
by the RTPU, and returns dot images and operator messages to buffers in
memory which the RTPU empties. Figure 2–10 summarizes the architecture
of the CCB.
PRINTER
INTERFACE
DATA PROCESSING
SHARED MEMORY
REAL–TIME
Common Controller Board
UNIT
PROCESSING
UNIT
PRINTING
MECHANISM
INTERFACE
(DPU)
(RTPU)
CONTROL PANEL
(CCB)
Figure 2–10. Architectural Overview of the CCB