EMC12 ETC2 [List of Unclassifed Manufacturers], EMC12 Datasheet - Page 38

• Manufacturer Part Number: EMC12
• Description: Audio Interface for the EmPack System
• Manufacturer: ETC2 [List of Unclassifed Manufacturers]

09 Jan 2006
The EmGetCodecCvMode function reads the current conversion modes and stores the results
in the memory pointed to by its InputCvMode and OutputCvMode arguments.
When using the 16-bit conversion modes, it is necessary to configure the TDM map to use pairs
of consecutive TDM slots to carry each 16-bit sample. This is accomplished by configuring the
TDM MAP using first a normal TDM slot connection, followed by a CONTINUATION slot in
the succeeding time slot.
Note that the linear 8-bit conversion for the CS4231A CODEC deals with unsigned values. This
is not directly compatible with the DSP32C’s iconv and oconv instructions which deal with
signed 8-bit values.
The EmSetCodecSampleRate function controls the sample rate of the CODEC. Valid values
for the SampleRate argument are defined as macros in the emapi.h. They are:
The TDM connections for the CODECs must be configured in accordance with the selected
sample rate. The EmPack TDM subsystem runs with a fixed frame rate of 8 kHz with 128 slots
per frame and 8-bits per slot. The simplest scenario is when the CODEC is set for 8 kHz
sampling rate; data must be transferred between the TDM subsystem and each CODEC channel
at a rate of one sample per TDM frame. However, at higher sampling rates multiple samples
must be transferred during each TDM frame and the transfers for each sample must occur
within certain fixed time slot ranges. The ranges of time slots for each sample depend on the
selected sample rate. Table 22, below, shows the valid TDM time slot ranges for each CODEC
data sample at the various sampling rates.
int
EmSetCodecSampleRate (
)
Sample
16 kHz
32 kHz
48 kHz
8 kHz
Rate
RESOURCE_HANDLE Resource,
int SampleRate
EM_CS4231_SR8
EM_CS4231_SR16
EM_CS4231_SR32
EM_CS4231_SR48
per Frame
Table 1-22: CODEC / TDM Transfer Mapping
Samples
1
2
4
6
Communication Automation Corporation
EMC12 Hardware Reference Manual
0 - 127
0 - 63
0 - 31
0 - 19
8 kHz Sample Rate
1
16 kHz Sample Rate
32 kHz Sample Rate
48 kHz Sample Rate
64 - 127
32 - 63
20 - 41
2
-
int
EmGetCodecSampleRate (
)
Time Slot Range for Sample:
64 - 95
42 - 63
RESOURCE_HANDLE Resource,
int *SampleRate
3
-
-
96 - 127
64 - 83
4
-
-
84 - 105
5
-
-
-
106 - 127
6
-
-
-
1-34