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GEN Routines: Line/Exponential Segment Generators

GEN05, GEN07

  f  #    time    size   5   a   n1   b   n2   c  .  .  .  
  f  #    time    size   7   a   n1   b   n2   c  .  .  .    

Description

These subroutines are used to construct functions from segments of exponential curves (GEN05) or straight lines (GEN07).

Initialization

size – number of points in the table. Must be a power of 2 or power-of-2 plus 1 (see f statement).

a, b, c, etc. – ordinate values, in odd-numbered pfields p5, p7, p9, . . . For GEN05 these must be nonzero and must be alike in sign. No such restrictions exist for GEN07.

n1, n2, etc. – length of segment (no. of storage locations), in even-numbered pfields. Cannot be negative, but a zero is meaningful for specifying discontinuous waveforms (e.g. in the example below). The sum n1 + n2 + .... will normally equal size for fully specified functions. If the sum is smaller, the function locations not included will be set to zero; if the sum is greater, only the first size locations will be stored.

Note

If p4 is positive, functions are post-normalized (rescaled to a maximum absolute value of 1 after generation). A negative p4 will cause rescaling to be skipped.

Discrete-point linear interpolation implies an increase or decrease along a segment by equal differences between adjacent locations; exponential interpolation implies that the progression is by equal ratio. In both forms the interpolation from a to b is such as to assume that the value b will be attained in the n + 1th location. For discontinuous functions, and for the segment encompassing the end location, this value will not actually be reached, although it may eventually appear as a result of final scaling.

Example

  f 1 0 256 7 0 128 1 0 -1 128 0

This describes a single-cycle sawtooth whose discontinuity is mid-way in the stored function.


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GEN Routines: Line/Exponential Segment Generators