f. The general theory of operation is provided as an introduction to the plotter
system at a simplified block diagram level. Input to the plotter is from a desktop
computer through an HP-IB Interface bus. The ADDRESS switch setting on the inter-
connect PCA determines the bus address that the plotter will respond to. When
addressed to transfer data or status, the HP-IB circuitry sets up the data transfer
and provides the interface between the plotter microprocessor and the controller.
(1) Data transfer is controlled by the processor circuitry which generates
the appropriate timing signals to properly sequence the processing of data and
instructions on the plotter bus.
(2) In the memory circuitry, the read only memories (ROMs) store the
instructions and data constants which the processor accesses and interprets. The
random access memories (RAMs) are used for temporary storage of microprocessor
c a l c u l a t i o n s a n d f o r i n p u t / o u t p u t d a t a .
(3) The internal I/O circuitry provides an interface between the front panel
PCA circuitry and the plotter bus and also passes velocity information from the
microprocessor to the motor drive circuitry.
( 4 ) T h e i n t e r p o l a t o r c i r c u i t s a c c e p t v e l o c i t y i n f o r m a t i o n g e n e r a t e d i n t he
processor and convert this information from digital format to the analog waveforms
required by the motor drivers for the X- and Y-axis motors.
(5) The motor drivers provide both voltage and power amplifications for the
analog signals generated by the interpolator circuits. These signals drive the X-
and Y-axis plotter motors.