TrueSpeech® Co-Processor
PRELIMINARY/CONFIDENTIAL
Version: 1.18
9 CT8022 Host Control Protocol
9.1 Operational Modes
It is possible to operate the CT8022 in eight main modes:
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Idle Mode
In this mode, the CT8022 transmit and receive buffers are empty. Data from the receive CODEC is ignored,
silence is output to the transmit CODEC.
Playback Mode
In this mode, the playback buffer is active and the TrueSpeech frame decompression function operates (if in
TrueSpeech mode). The Host should provide data for output in this mode. If no data is available, the most
recent frame present in the playback buffer is replicated, and output until new data is available. By default,
speech is output via CODEC 1.
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Record Mode
In this mode, the record buffer is active and the TrueSpeech compression function inserts speech frames into
the record buffer (if in TrueSpeech mode). The Host should extract frames from the CT8022 in this mode. If
the Host does not take data from the CT8022, the record buffer will fill, and then frames will be discarded.
By default, speech is input via CODEC 1.
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Full Duplex Speech Mode
This mode is equivalent to the playback and record modes operating concurrently.
CODEC Loopback Mode
This mode provides a test mode which enables CODEC-input to CODEC-output loopback.
Line Monitor Mode
In this mode, the CT8022 provides DTMF and Call Progress Tone detection. These services are also
available during record and playback operations.
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Full Duplex Speech Mode plus Acoustic Echo Canceller (AEC) (DSVD Speakerphone Mode)
In this mode, the AEC is active and attempts to remove the acoustic echo of the speaker output that is picked
up at the microphone input.
Full Duplex (Standalone) Speakerphone Mode
In this mode, the CT8022 operates as a Full Duplex Speakerphone using an analog telephone line connection.
This requires operation with two external CODECs. The CODEC0 connection must be used for the
telephone line audio (analog) input/output. The CODEC1 connection must be used for the speaker-
microphone audio input/output. In Full-Duplex Speakerphone mode, the CT8022 attempts to cancel the
speaker-to-microphone acoustic echo and also the telephone line transmit to telephone line receive electrical
echo.
Note: The terms Standalone Speakerphone and DSVD Speakerphone are used throughout this document to
distinguish between conventional analog telephone Speakerphone operation and Speakerphone
operation in a hands-free DSVD or Video Conferencing system (compressed digital speech via a
modem or LAN).
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DSP GROUP, INC., 3120 SCOTT BOULEVARD CT8022A11AQC FW Revision 0118
SANTA CLARA, CA 95054 PH: 408 986 – 4300 FAX: 408 986 – 4490
All specifications are subject to change without prior notice.
ETC [ ETC ]
