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CHAPTER 8
THE MDFG
8
0
1
INTRODUCTION
The MDFG allows the generation of arbitrary continuous non-linear functions
by means of straight-line segment approximation.
Both ten and twenty seg-
ment operations are possible.
8.2
LOCATION
AND
ADDRESSING
A
fully expanded 580 contains 8 ten-segment DFG's.
The DFG's are arranged
in pairs, and each pair may be used as a twenty-segment DFG or as two ten-
segment DFG's.
The DFG's are located in slideout drawers directly below
the analog patch panel.
Each pair of DFG's are terminated on a single patch block in the analog
patching area.
To address a DFG for readout, it is necessary to depress
the F pushbutton and the numerical address on the main control panel.
The
address for each of the MDFG pairs is F46, 47, F56, 57, F66, 67, and F76,
77.
In a ten-segment operation each
MDFG
is addressed using one of the ad-
dresses given above.
In a twenty-segment operation the first DFG in each
pair (the one ending in -6) uses all twenty segments leaving the output am-
plifier of the second DFG (the one ending in -7) available as an inverter.
In a standard computer configuration, the first DFG in a pair is the +DFG,
capable of accepting positive inputs.
The second DFG is a -DFG, capable
of accepting negative inputs.
Either type of DFG can produce either posi-
tive or negative outputs.
Figure 8.1 shows the MDFG patching terminations
on a separate tray (8.la) and the patching terminations on a mUlti-purpose
tray (8 .lb).
8.3
APPLICATIONS
The main application for a DFG is function generation; however, the inclu-
sion of an additional input resistor for each DFG allows some alternate
applications such as the use of the unused output amplifier as an inverter,
and combined summation and function generation.
8
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4
SETUP PROCEDURE
Since the diode function generator approximates a given curve by'a series
of straight-line segments, the first step in the setup of any DFG is to de-
termine the location of the breakpoints ("corners") in order to fit the
curve as smoothly as possible.
Usually the desired curve is given in graphi-
cal form, and the programmer must determine, by inspection of the graph, a
table of values of x and f{x) for setup.
Sometimes the function is given
in tabular form - a table of values of x and f(x).
Such a table o'f values
is usually the result of experimental measurements, although it may repre-
sent the result of a series of calculations.
8-1
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