Digital Voice Systems VC-20-PRJ25, Руководство пользователя

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VC-20-PRJ25 IMBE™ Vocoder Board
User’s Manual
Page 7
Section 3 – Technical Specifications
DVSI Confidential Proprietary
GND,
AGND
GND is the digital ground signal and AGND is the analog ground signal. These signals
are connected on the VC-20-PRJ25.
HD_SD The HD_SD signal must be set low to enable soft-decision decoding. This signal is
sampled once every 20 ms data frame. If left unconnected, this signal is pulled internally
to its inactive state (high).
IRXD,
IRXD1, and
IRXD0
IRXD, IRXD1, and IRXD0 are the in-phase data signals. These signals provide three
bits of soft-decision information, with IRXD being the MSB and IRXD0 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 quadrature-phase data
signals result in a total data rate of 7.2 kbps.
ITXD and
QTXD
ITXD and QTXD are the in-phase and quadrature-phase voice data signals from the
VC-20-PRJ25 encoder. These signals are each clocked at 3.6 kHz, giving a total data
rate of 7.2 kbps.
LOST The LOST flag is active if the current frame of channel data is invalid, in which case the
decoder ignores the current frame of channel data and performs a frame repeat. This
flag is only monitored during the first clock period of each frame.
RESET The RESET signal is a software flag that indicates that the voice codec had been reset
or that the encoder had lost synchronization. The VC-20-PRJ25 is reset under three
conditions: during power-up, as a result of DINRS being asserted, or as a result of a
Watch-Dog Timer reset. When the VC-20-PRJ25 successfully restarts from a reset or
a loss of encoder synchronization, it will set the RESET flag high for one clock cycle of
TXCK. This flag is synchronous with the rising edge of TXCK. RESET is a software
flag; whereas, RESX is the hard-reset signal.
RESX RESX is the reset status output signal. It is active when the VC-20-PRJ25 is being
reset. The VC-20-PRJ25 is reset under three conditions: during power-up, as a result
of DINRS being asserted, or as a result of a Watch-Dog Timer reset. This signal is an
active low output. RESX is the VC-20-PRJ25's actual hard-reset signal; whereas,
RESET is a software flag that is synchronous with TXCK.
RUN RUN is a status signal that signifies that the VC-20-PRJ25 is encoding and decoding
speech. This signal drives the green RUN LED. Each data frame is divided into an
encoder window and a decoder window. The RUN signal is active within each
respective window when the VC-20-PRJ25 is encoding or decoding speech (see figure
6). RUN is synchronous with TXCK.