434 WM-OM-E Rev I
possible error
messages:
"TRELLIS_LENGTH must be >= 11 and <= 81"
keyword:
ZERO_CROSS_TO_SAMPLE
arguments:
<value 0 to 0.5>
required?:
yes
Notes:
This tells the DDA how the correct sampling times relate to zero crossings during the VCO
synchronization preamble. The value is a fraction of the spacing between zero crossings. Example:
The VCO synch is normally a 2T pattern. For PR4 the samples are 1, 1, -1, -1; there are two samples
between zero crossings, and the first sample after a zero crossing is one quarter of the distance to the
next zero crossing. Therefore ZERO_CROSS_TO_SAMPLE is 0.25 for PR4. For EPR4, a 2T pattern
gives samples 0,1,0,-1; the first sample is at the zero crossing; therefore,
ZERO_CROSS_TO_SAMPLE is 0 for EPR4. For E2PR4, a 2T pattern gives 2/3, 2/3, -2/3, -2/3; there
are two samples between zero crossings, and the first sample after a zero crossing is one quarter of
the distance to the next zero cross, just as for PR4. Therefore ZERO_CROSS_TO_SAMPLE is 0.25
for E2PR4.
possible error
messages:
"ZERO_CROSS_TO_SAMPLE must be >= 0 and <= 0.5"
Example File
An example of a user definition equivalent to E2PR4 (d=0) follows. This file was named
E2PR4.UDF:
USER DEFINED VITERBI TRELLIS FOR LECROY DDA // a comment can go here
// The above line is required exactly as shown or the file will be rejected!
KEYWORDS_VERSION 1
STATES 16
// State initializers - one for each valid state
// state prev from 0 level prev from 1 level
STATE 0 0 0 8 -0.33333
STATE 1 0 0.33333 8 0
STATE 2 1 0.66667 9 0.33333
STATE 3 1 1 9 0.66667
STATE 4 2 0 10 -0.33333
STATE 5 2 0.33333 10 0
STATE 6 3 0.66667 11 0.33333
STATE 7 3 1 11 0.66667
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