A N A L Y S I S B O A R D - Philips SPENDEX 40 Maintenance Manual

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NATO CONFIDENTIAL
S P E N D E X 4 0 U A 8 2 5 1 / 0 0 A N D / O l L I M I T E D M A I N T E N A N C E M A N U A L
4 . 5 A n a l y s i s b o a r d
4 . 5 . 1 S e g m e n t a t i o n b u f f e r
The A/D-converter on the connecting board presents the in a-law coded
8-bit samples in serial form to the segmentation buffer. In the
segmentation buffer a speech segment of 256 samples can be stored.
Every 22.5 ms 180 samples are changed and the total contents of the
buffer are read out and passed on 128 times parallel to the DFT-
processor. During the first transfer to the DFT-processor the speech
segment is stored in the speech buffer at the same time.
4 . 5 . 2 P i t c h b u f f e r
The pitch buffer is an 8-bit buffer for the temporary storage of the
p i t c h .
4 . 5 . 3 S p e e c h b u f f e r
In the speech buffer 4 speech segments of 256 samples can be stored
and every time the oldest speech segment is overwritten by a new one.
4 . 5 . 4 A n a l y s i s p r o c e s s o r
As soon as a new speech segment has been written into the speech
buffer, the analysis processor collects the pitch from the pitch
buffer and the LPC-analysis of the oldest speech segment in the
speech buffer is started. The results of the LPC-analysis are put in
a 54-bit frame. The moment the analysis processor has a new frame
ready, the vocoder controller is interrupted (INTAN). After
acceptation of the interrupt the vocoder controller will take over
the frame and store it in the analysis part of the vocoder data
memory on the synthesis board.
4 . 5 . 5 T i m i n g c i r c u i t
The timing circuit generates several timing signals for the control
of the various circuits within the vocoder.
4 . 5 . 6 S l a v e c l o c k s i g n a l g e n e r a t o r
The slave clock signal generator is controlled by the master clock
signal generator on the synthesis board. The slave clock signal
generator produces clock signals of 4096 kHz and 2048 kHz. These
clock signals control various circuits within the vocoder.
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NATO CONFIDENTIAL