TrueSpeech® Co-Processor
PRELIMINARY/CONFIDENTIAL
Version: 1.18
9.7.3
Peak Level Indication
The PEAK bit in the S2 status response is set if the average input level for the current speech frame exceeds the
threshold configured using the Set Peak Threshold command. The Host can use this bit to perform silence detection
during recording. Note that the record signal level can also be accessed using the Read Record Level command.
This is the recommended method of determining the record input signal level, when TFR Mode = [binary] 11 and
the C2-S2, C3-S3 sequence is not used.
9.7.4
Record Protocol
Example 1: TrueSpeech 6.3 Record via Host Receive Data Buffer Access Port - Host Polling
This example shows how to start recording using TrueSpeech 6.3 with data transfers performed via the Host Receive
Data Buffer Access Port. The Host controller performs all data transfers in this example. The Host polls the
Hardware Status Register to synchronize data.
Starting Record
1. CT8022 is in IDLE or PLAYBACK state.
2. Host checks for CONTROL READY state in Hardware Status Register.
3. Host selects TrueSpeech 6.3 recording by writing the Select TrueSpeech Record Rate command = 5131H to the
Software Control Register.
4. CT8022 responds via the Software Status Register
5. Host waits for STATUS READY indication in the Hardware Status Register, then reads the CT8022 response
from the Software Status Register. This clears the STATUS READY bit.
6. Host selects Poll Sync Mode for record using the command 5102H.
7. CT8022 responds via the Software Status Register.
8. Host waits for STATUS READY indication in the Hardware Status Register, then reads the CT8022 response
from the Software Status Register. This clears the STATUS READY bit.
9. Host selects Record by issuing the RECORD C1 command = 1C03H via the Software Control Register. This
also informs the CT8022 that data transfers will occur via the Host Receive Data Buffer Access Port (TFR
Mode = [binary] 11 ).
10. CT8022 performs internal synchronization then responds with the RECORD S1 status response after a delay of
up to 2 speech frame periods.
11. Host waits for STATUS READY indication in the Hardware Status Register, then reads the CT8022 response
from the Software Status Register. This clears the STATUS READY bit.
12. The CT8022 is now in record mode. The CT8022 will produce a compressed speech frame every 30ms
(assuming the base frame size is set to 240). The following sequence is used to transfer each compressed speech
data frame from the CT8022 to the Host:
a. Host waits for the RX Ready bit to be set in the Hardware Status Register
b. Host reads 12 words (for TrueSpeech 6.3) from the Host Receive Data Buffer Access Port.
Note: For transfer of speech blocks larger than 16 words via the Host Receive Data Buffer Access Port, the
transfer will be split into sub-blocks of 16 words each or less. The CT8022 will create a small pause
between each sub-block during which it will re-fill the data access port (approximately 5
microseconds).
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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 ]
