RALCWI Vocoder
CMX608/CMX618/CMX638
Supporting other CODECs
CODECs other than the two detailed above can be used with this device, providing they meet the basic
capabilities mentioned above.
There are three facts that must be established in order to successfully use a CODEC:
.
Is the data sampled on the positive or the negative edge of the SCLK?
If the data is sampled on the positive edge of SCLK, choose either CODEC_GENERIC1
or CODEC_GENERIC2 as the CODEC type. If the data is sampled on the negative edge
of SCLK, then choose either CODEC_GENERIC3 or CODEC_GENERIC4 as the CODEC
type.
.
Does the CODEC output 16 or more SCLKs before a frame sync?
If the CODEC outputs less than 16 SCLKs before the first frame sync, choose
CODEC_GENERIC2 or CODEC_GENERIC4 as the CODEC type. If the CODEC outputs
16 SCLKs or more before the first frame sync, then choose CODEC_GENERIC1 or
CODEC_GENERIC3 as the CODEC type.
The CODEC type to use is the choice that is common to both of the above.
Does the CODEC require data to be sent to it for configuration?
.
If the CODEC requires configuration words to be sent to it to set it up, these should be
loaded into the CODEC command FIFO.
Hardware control of the CODEC can be done by using the EEC and REC output pins. Either use the
direct control commands REC/EEC (0,1,2,3) or use the individual control commands
ECC_???_LOW/ECC_???_HIGH ($89-$8C). Using the generic CODEC settings means that the
ECC_CODEC_RESET/ECC_CODEC_START/ECC_CODEC_PSAVE commands do nothing and
therefore should not be used.
5.7.
Operation with DTMF (Dual Tone Multi-Frequency)
The CMX608, CMX618 and CMX638 (in half-duplex mode only) can be enabled to send or receive DTMF.
This facility is not available when the CMX638 is used in full-duplex mode.
5.7.1.
DTMF Transmit
When the device is transmitting voice data (encoding), special DTMF data frames can replace the voice
data frames. The DTMF data frames can be generated by one of two modes:
Mode 1
Mode 2
DTMF (Tones) are detected and decoded to a 4-bit number. This 4-bit number is sent in
the special DTMF data frames. In this mode, DTMF transmission is automated, i.e. if DTMF
is detected then the DTMF data frame is sent, otherwise the voice data frames are sent.
This mode is enabled by bit 11 (EDTMFD) in the VCTRL register ($11).
DTMF (Data) is entered directly as a 4-bit number in bits 0 to 3 of the SDTMF register ($08).
This 4-bit number is sent in the special DTMF data frames. In this mode, the duration of the
DTMF data frames is specified (in terms of the number of frames) in bits 4 to 7 of the
SDTMF register. Setting the duration to $0 disables this feature. Setting the duration to $F
enables continuous DTMF.
If both modes are enabled then Mode 2 will take precedence.
5.7.2. DTMF Receive
When the device is receiving voice data (decoding), special DTMF data frames may replace the voice data
frames. If DTMF is enabled in receive then DTMF data frames are automatically detected and can be
used in one of two modes:
2014 CML Microsystems Plc
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D/608_18_38/11
CMLMICRO [ CML MICROCIRCUITS ]
