TM 5-6675-320-14
4-3.2.3 Data Processing.
I s t h e “ b r a i n ” o f t h e p l o t t e r . A l l t i m i n g a n d c o n t r ol
is initiated here and data is converted to a usable form for driving (controlling)
the analog pen drive circuits.
Data processing consists of three PCA cards:
Processor PCA card A3
Memory PCA card A4
Internal I/0 PCA card A5
Each of these circuit cards performs its own set of functional operations as part of
the overall function of the data processing.
a.
Processor PCA card A3.
Provides the timing signals for all operations that
occur in the plotter, synchronizing dependent events to a common clock. The
processor also performs mathematical manipulation of the input data to convert it to
p l o t t e r i n t e r n a l c o n t r o l l a n g u a g e.
PCA A3 consists of a microprocessor, local ROM,
a n d s u p p o r t c i r c u i t s .
Each operation that the microprocessor performs is controlled
by a program of instructions prestored in ROM on PCA A4.
PCA A3 performs three functions:
Timing.
C o n t r o l s t i m i n g f o r a l l p l o t t e r o p e r a t i o n s.
Information processing .
Utilizes programmed instructions to
request data, manipulate data and transmit data to appropriate
c i r c u i t s .
S e l f - t e s t .
Initiates and controls preprogrammed self-tests.
( 1 ) T i m i n g.
Is controlled by the clock generator which establishes the time
base.
The clock generator consists of U27, crystal Y1, and associate passive ele-
ments.
The clock frequency is divided in two by flip-flop U25. A 180 degree
phase shift occurs here because the output comes from the Q+ and Q- outputs. The
phase clock driver provides phase 1 and phase 2 clocks. Phase 1 clock is high when
phase 2 clock is low.
These two clocks provide for the synchronous operation of the
p l o t t e r .
( 2 ) I n f o r m a t i o n p r o c e s s i n g .
Establishes the movement of data within the
p l o t t e r .
The microprocessor controls the flow of data on PCA A2 and PCA A5. The
processor receives vendor data from the computer via PCA A2, interprets it, and
sends velocity commands to PCA A5 for positioning of the pen.
(a) In order for the microprocessor to perform these functions, it must
be instructed in a step-by-step procedure for each different operation it performs.
These sets of instructions are permanently stored in ROMs on PCA A4.
(b) The microprocessor reads instructions from ROM phases (U21 and U22)
on PCA A3 and other ROM and RAM located on PCA A4. It also can write into RAM for
temporary storage of data.
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