TrueSpeech® Co-Processor
PRELIMINARY/CONFIDENTIAL
Version: 1.18
9.24.4
CT8022 Slowdown (Power Save) Modes
The Host can program the CT8022 to enter slowdown mode. In slow down mode, the clock rate of the internal DSP
core is reduced to allow sufficient processing power for the operation selected. For example, when the CT8022 is
performing full-duplex TrueSpeech 6.3 operation in conjunction with AEC operation, the DSP core must be run at
full speed. However, when the CT8022 is being used in pass-through mode to playback uncompressed 16-bit linear
data, the DSP core can be operated at greatly reduced speed.
To enter slow-down mode use the following command:
Command
Status
= 0FEXH where X is the internal DSP clock division factor
= 0FEXH
The internal DSP core clock is divided by (X+1), such that:
X=0 selects full speed
X=1 selects 1/2 speed
X=2 selects 1/3 speed
X=3 selects 1/4 speed
X=F selects 1/16 speed
The internal DSP clock frequency can be observed on the CLKOUT pin.
The following table gives an approximate guide to the processing speed required for some sample operations:
Operation
X Value
DSP Internal Speed
Factor
Typical Power
Consumption
Full-duplex TrueSpeech 6.3-4.1 + AEC
Full-duplex TrueSpeech 8.5 + AEC
Playback only (all modes)
Full Duplex uncompressed speech
Line Monitoring (tone detection)
IDLE
0
1
3
3
3
F
1.0
1/2
1/5
1/5
1/5
230 mA
120 mA
60 mA
60 mA
60 mA
35 mA
1/16
AEC = Acoustic Echo Canceller
9.24.5
Disable CLKOUT
To further conserve power and reduce EMI emissions, the CLKOUT signal of the CT8022 may be disabled with the
following command:
Disable CLKOUT
Command: 0FF6H
Status:
0FF6H
Enable CLKOUT
Command: 0FF7H
Status: 0FF7H
156
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 ]
