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PRINCIPLES OF OPERATION
6.7 l/O (Input/Output)
Circuitry
The I/O circuitry
interfaces
the microcomputer
to the
display, keyboard, the analog outputs,
real time output
serial control, and the NV (non-volatile RAM). A schematic
diagram of this circuitry may be found on drawing number
194.166 located at the end of Section 8.
6.7.1 l/O Block Diagram
Figure 6-8 shows a simplified
block diagram of the in-
put/output
circuitry. Circuit operation centers around three
peripheral KS which perform many of the interfacing func-
tions. Two PIAs (Peripheral Interface Adapter) provide the
interface to the front panel display. These ICs also provide
the interface to the NVRAMs
located on the A/D. The
primary function
of the VIA (Versatile Interface Adapter)
is to interface the MPU to the keyboard circuits. This IC
also provides the serial control interface on the real time
output.
The data latches store data to be used by the real time
analog outputs. For the X and Y outputs, data is converted
to analog form by IZ-bit DACs (Digital-to-Analog
Con-
verters). No DAC is necessary for the Z output as that out-
put assumes only one of two logic levels, high or low,.
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6-19
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