Digital Voice Systems VC-20-PRJ25, Руководство пользователя

Страница: 16 / 25

VC-20-PRJ25 IMBE™ Vocoder Board
User’s Manual
Page 8
Section 3 – Technical Specifications
DVSI Confidential Proprietary
RXCK This is the decoder symbol clock which controls the transfer of the channel data into the
decoder. This signal must be 3.6 kHz +/- .05%. IRXD, IRXD1, IRXD0, QRXD,
QRXD1, QRXD0, FMDE, LOST and DESLNCE are synchronous with the rising
edge of this clock signal to within 500 ns.
QRXD,
QRXD1,
and
QRXD0
QRXD, QRXD1, and QRXD0 are the quadrature-phase data signals. These signals
provide three bits of soft-decision information, with QRXD being the MSB and
QRXD0 being the LSB. If the HD_SD control signal is low (soft-decision mode
enabled), then all three data signals are read by the decoder. If HD_SD is high, then
only IRXD (the MSB) is read by the decoder. These signals are each clocked into the
VC-20-PRJ25 on the falling edge of RXCK at 3.6 kHz. These signals combined with
the in-phase data signals result in a total data rate of 7.2 kbps.
STATUS The STATUS flag indicates the status of the voice codec. During normal operation, the
voice codec sets this flag high for one clock cycle of TXCK every data frame.
Absence of this signal during any data frame indicates an error condition. This flag is
synchronous with the rising edge of TXCK.
TXCK This is the encoder data clock which controls the transfer of the channel data out of the
encoder. This signal must be 3.6 kHz +/- .05%. ITXD, QTXD, FMEN, ENSLNCE,
RESET, STATUS, and RUN are synchronous with the rising edge of this clock signal
to within 500 ns.
VFRO VFRO is the analog speech output produced by passing the decoder output through a
16 bit linear codec. VFRO has an analog bandwidth of 100 Hz. - 3600 Hz., and it is
constrained to be /- 1.5 volts.
VRXI
VFXI is the analog speech input which is filtered with a 100 Hz. - 3600 Hz. bandpass
filter and then input to the encoder via a 16 bit linear codec. In order to avoid clipping
VRXI must not /- 1.5 volts.