Digital Voice Systems VC-20-ATC-10B Especificaciones descargar pdf (Pagina 49)

FAA20 Embedded NEXCOM Vocoder

Board Manual

This manual has been prepared for the Federal Aviation Administration.

FA100-00107 (March 2004) – Rev 1.0.0 Page 43

tasks are triggered by different events. If the event timing is not directly

related, timing differences can cause the accumulation/depletion of voice

samples. For example, the AUD_HWI timing is derived from the FAA20

DSP clock and the nibble interface is externally timed, the timing references

are not related. For most queues, if the packet ready or empty size is one

less than required, a sample is added (repeated) or dropped, respectively.

When the vocoder functions (ENC_SWI and DEC_SWI) access the queue,

the built-in, linear window size, calling parameter is used (see DVSI

software vocoder documentation).

For some configurations, SPAD events are normal. For example, when the

analog interface is used with the vocoder and external nibble timing is

enabled, SPAD events normally occur somewhere in the voice path.

Alternatively, when the PCM interface is used with the vocoder and external

timing is used for both the PCM and nibble interface, SPAD events should

not occur.

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Digital Voice Systems VC-20-ATC-10B Especificaciones Pagina 49