Version: 1.18
PRELIMINARY/CONFIDENTIAL
TrueSpeech® Co-Processor
9.23.5
CODEC Loopback
The CT8022 supports CODEC-input to CODEC-output loopback, independently of the test modes described
previously. In this mode, every frame period (30ms), the CT8022 will loop-back 240 samples from the input
CODEC back to the output CODEC. To enter this mode, the CT8022 must be in the IDLE state. To activate this
mode use the command:
Command
Status
= 4000H
= 4000H
This loop-back mode can be used in conjunction with Test Mode 2 (Section 9.23.2) to generate a digital milliwatt
output signal to the CODEC.
The CODEC Configuration command can be used to select the input and output CODECs used for the loop-back
operation. For example, the following CODEC routings are possible:
Input Signal
From
Output Signal
To
CODEC Configuration Command
Output CODEC
Input CODEC
CODEC1
CODEC1
CODEC0
CODEC0 & 1
CODEC0
CODEC1
00
10
11
10
00
11
0
0
0
1
1
1
CODEC1
CODEC1
CODEC0
CODEC0
CODEC0
CODEC0 & 1
The Input CODEC field operates to exchange (swap) the input signals from CODEC0 and CODEC1.
Use of this form of loopback operation requires that the CT8022 be in the IDLE state when the command to activate
loopback is issued. This loopback configuration cannot be used in conjunction with other CT8022 operational
modes (e.g. playback and record). To perform loopback type operations in record or playback, refer to Section
9.23.6.
To exit loopback mode, the Host should issue the Idle command (0000H).
CT8022A11AQC FW Revision 0118 DSP GROUP, INC., 3120 SCOTT BOULEVARD
SANTA CLARA, CA 95054 PH: 408 986 – 4300 FAX: 408 986 – 4490
153
All specifications are subject to change without prior notice.
ETC [ ETC ]
