RALCWI Vocoder
CMX608/CMX618/CMX638
Bit 12
ESTDD
Encoder STD Detect: If this bit is set to '1', the encoder will try and detect single
tones in the input audio stream. If a single tone is detected, the encoder will form
a special STD frame and place the frequency of the detected single tone in the
EFRAMEDATA register ($38). If a single tone is not detected the audio will be
passed on to the next stage.
If this bit is cleared to '0', the encoder will treat the signal as voice and will not
detect single tones.
If this bit is set to '1', then the DSTDD bit in the decoder at the other end of the
channel should also be set to '1'. See section 6.4 for further details.
Bit 13
ESTDP
Encoder STD Priority: Controls the order of the audio processing in the encoder.
Single tone detection and DTMF detection are separate stages that are performed
on the input audio stream before being given to the Vocoder to encode.
If this bit is set to '1', the encoder will first try and detect a single tone before trying
to detect DTMF.
If this bit is cleared to '0', the encoder will first try and detect DTMF before a single
tone.
This bit is only significant if both ESTDD and EDTMFD bits are set to '1'. If either
bit is cleared to '0', then the ESTDP bit is ignored.
Bit 14
This bit must be cleared to '0' for correct operation.
Bit 15
This bit must be cleared to '0' for correct operation.
EXCODECCMD register address $12
15 14 13 12 11 10
9
8
7
6
5
4
3
2
1
0
External CODEC command word
This write-only register enables initialisation commands to be sent to an external CODEC.
The Vocoder device has a FIFO, 16 words deep, to hold initialisation commands for an external
CODEC. Each write to this register pushes its contents into this FIFO and increments the FIFO
word counter. After the word has been pushed into the FIFO, bit 15 (RDY) of the STATUS register
($40) will be set and, if enabled, IRQN will go low. No other C-BUS registers should be read or
written whilst this operation is in progress.
When the device is RESET, this FIFO will be empty. Once filled, the contents will remain in the
FIFO until a RESET or explicitly emptied by writing the ECC_FIFO_CLEAR command to the
EXCODECCONT register ($0B). This allows the re-use of the initialisation sequence if the
CODEC needs to be reset for any reason.
The count of words currently in the FIFO may be read from the ECFIFO register ($24) after this
command has completed, which is indicated by SVCACK register ($2E) bit 0 being set to '1'.
After starting the SSP, all the words in the FIFO will be sent to the device. Once all the words are
sent, the Vocoder device will assume that the CODEC is now running and that all data transferred
are audio samples.
2014 CML Microsystems Plc
48
D/608_18_38/11
CMLMICRO [ CML MICROCIRCUITS ]
