CMX649 CML Microcircuits, CMX649 Datasheet - Page 30

• Manufacturer Part Number: CMX649
• Description: ADM Codec
• Manufacturer: CML Microcircuits

ADM Codec
DECODE ADM INPUT Register ($D8)
Decoder ADM
Input
(Bits 7 – 0)
ENCODER MODE AND SETUP Register ($E0)
Decimation
Rate (by 4/8)
(Bit 15)
PCM Input
Select
(Bits 14 – 13)
ADM Input
Select
(Bits 12 – 11)
2003 CML Microsystems Plc
This register allows ADM bits to be written into the decoder via C-BUS and is
intended for transcoding. Bit 0 of the CODEC INTERRUPT CONTROL Register
($81) can be set to a logic 1 to enable interrupts informing a micro-controller when
the register should be updated. Additionally this register can be loaded with an idle
data pattern ($55 or $AA) and then selected as the input to the decoder via the
DECODER MODE AND SETUP Register ($D0)
The encoder PCM filter functions as a decimating lowpass when the encoder is
running. PCM values are available in the ENCODE LINEAR PCM OUTPUT
Register ($E6) at the decimation rate. A logic 1 sets the decimation rate to 4 (1/4
the bit rate).
A logic 0 sets the decimation rate to 8 (1/8
Allows selection of the input to the PCM rate converting filter.
If PCM filter is interpolating, the encoder can transcode a PCM signal to ADM.
If PCM filter is decimating, the encoder will transcode an ADM signal to PCM.
Bit 14
Bit 12
0
1
1
0
0
1
Bit 13
Bit 11
X
X
0
1
0
1
PCM filter decimates ADM estimator output
PCM words available in register $E6.
PCM filter interpolates PCM input from burst
mode interface (RX DATA pin).
This selection must be made in conjunction
with the CODEC MODE CONTROL Register
($70).
PCM filter interpolates PCM input from C-
BUS interface via the ENCODE DAC TEST
CONTROL Register ($E7).
ADM encoder input from Comparator.
(Normal mode operation).
ADM encoder gets input from C-BUS
breaking the feedback loop and allowing the
local decoder to digitally transcode an ADM
signal input via C-BUS to a PCM signal
output via C-BUS or the burst interface.
(Alternate ADM input operation).
ADM input from transcode feedback. When
ADM input comes from transcode feedback
it will transcode from PCM to ADM. The
PCM filter must be set to interpolate. In this
mode the encode analog interface can be
powered down since it is not used.
(PCM to ADM transcoding input operation).
30
Selected ADM Input
Selected PCM Input
th
the bit rate).
CMX649
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