CT8022 Datasheet, PDF (73/194 Pages) List of Unclassifed Manufacturers – VOIP/VON G.723.1, G279AB TRUESPEECH CO-PROCESSOR

Version: 1.18
PRELIMINARY/CONFIDENTIAL
TrueSpeech® Co-Processor
9.8.3
Playback Protocol
Example 1: TrueSpeech 6.3 Playback via Host Transmit Data Buffer Access Port - Host Polling
This example shows how to start playback with TrueSpeech 6.3, using data transfers performed via the Host
Transmit 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 Playback
1. CT8022 is in IDLE or RECORD state.
2. Host checks for CONTROL READY state in Hardware Status Register.
3. Host selects TrueSpeech 6.3 playback by writing the Select TrueSpeech Playback Rate command = 5231H 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 playback using the command 5202H.
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 Playback by issuing the PLAYBACK C1 command = 2C03H or 2C01H via the Software Control
Register. This also informs the CT8022 that data transfers will occur via the Host Transmit Data Buffer Access
Port (TFR Mode = [binary] 11 or 01).
10. CT8022 responds via the Software Status Register 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 S1 = 2C03H or 2C01H. This clears the STATUS READY bit.
12. Host writes PLAYBACK C2 command = 2000H to the Software Control Register.
13. CT8022 responds via the Software Status Register.
14. Host waits for STATUS READY indication in the Hardware Status Register, then reads the CT8022 response
from the Software Status Register S2 = 2000H. This clears the STATUS READY bit.
15. Host writes PLAYBACK C3 command = 200CH to the Software Control Register. This command includes the
requested number of words per frame to transfer. In this case (TrueSpeech 6.3) this is 12 = 0CH.
16. CT8022 responds via the Software Status Register.
17. Host waits for STATUS READY indication in the Hardware Status Register, then reads the CT8022 response
from the Software Status Register S3 = 200CH. This clears the STATUS READY bit.
18. The CT8022 is now in playback mode. The CT8022 will be ready to consume 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 frame from the Host to the CT8022:
a. Host waits for TX Ready bit to be set in the Hardware Status Register
b. Host writes 12 words (for TrueSpeech 6.3) to the Host Transmit Data Buffer Access Port.
Note:
For transfer of speech blocks larger than 16 words via the Host Transmit 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 move the sub-block from the data access port
(approximately 5 microseconds).
The CT8022 can buffer up to 20 TrueSpeech 6.3 speech data frames (600ms). At the start of playback, the CT8022
will keep re-asserting the TX Ready condition until the internal 480 byte buffer is full, and the CT8022 has
pre-fetched 20 frames. If the Host must reduce the number of speech data frames pre-fetched by the CT8022, it can
do so using the playback Set Buffer Depth command (528XH). This can be set to reduce the effective size of the
internal buffer.
CT8022A11AQC FW Revision 0118
DSP GROUP, INC., 3120 SCOTT BOULEVARD
73
SANTA CLARA, CA 95054 PH: 408 986 – 4300 FAX: 408 986 – 4490
All specifications are subject to change without prior notice.