RALCWI Vocoder
CMX608/CMX618/CMX638
VCFG register address $07 (also MVCFG register address $2C)
7
6
5
4
3
2
1
0
DTMFF
DTX
HDD
FEC
BITRATE
FRAMES
This write-only register controls the configuration of the Vocoder. Certain aspects of the Vocoder
will be set up and initialised. The VCFG register is mirrored by the MVCFG register ($2C). This
read-only register holds the last value written to the VCFG ($07) register. The MVCFG register is
updated before the value is validated and therefore may be used as confirmation that a write
command to a 8-bit C-BUS register is working.
The VCFG command should only be issued when the device is not actively encoding, decoding or
performing an FEC loop, i.e when bits 0 to 2 of the VCTRL register ($11) are '0'. After this
command has completed, bit 15 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 command is in
progress.
If the command was successful, the value '1' will be written into the SVCACK register ($2E).
If the command was unsuccessful due to an invalid bit rate or due to it being issued when the
device is active, the value '0' will be written into the SVCACK register.
Also see Table 6 and Table 7 for a description of the VCFG register configuration for the various
decoder and encoder packet sizes.
Bits 1 and 0
FRAMES
Specifies the number of 20ms frames transferred according to the following table:
Bit 1
Bit 0
Description
0
0
1
1
0
1
0
1
4 off 20ms frames
1 off 20ms frames
2 off 20ms frames
3 off 20ms frames
Bits 3 and 2
BITRATE
Specifies the Vocoder bit rate according to the following table:
Note that programming both bit 2 and bit 3 to '1' will cause this command to fail.
i.e. An invalid bit rate.
Bit 3
Bit 2
Description
0
0
1
1
0
1
0
1
2050 bits per second
2400 bits per second
2750 bits per second
Not used
Bit 4
FEC
If this bit is set to '1', an FEC encoded packet will be produced by the encoder,
and an FEC encoded packet will be expected by the decoder. If this bit is cleared
to '0', packets of raw Vocoder frames will be produced and expected.
FEC is only available when 3 or 4 frame packets are being transferred. This bit
will be ignored for any other frames setting. See also section 6.2.
2012 CML Microsystems Plc
36
D/608_18_38/10
CMLMICRO [ CML MICROCIRCUITS ]
