Digital PMR Radio Processor
CMX7131/CMX7141
6.4
NXDN Standard Vocoder Interface
For the NXDN standard vocoder all radio channel data will need to be transferred over the main C-BUS
through the host. In this case the Vocoder 1 Enable Program registers (P1.11 and P1.12) should be set
appropriately and the SPI-Codec ENA bit ($B1 bit 0) should be set to 1.
The connections for the NXDN standard vocoder are shown in Table 11.
Table 11 NXDN Standard Vocoder Connections
CMX7131/CMX7141 Pin:
SSOUT
EPSI
AMBE-3000 Vocoder Device Pin:
SPI_STE
SPI_RX_DATA
EPSO
SPI_TX_DATA
EPSCLK
SPI_CLK and SPI_CLK_IN.
6.4.1 Support for I2S Mode
The device can support I2S interfaces in mono, 16-bit mode only, for transmitting and receiving audio
codec data using the SPI bus. This mode is selected in block 1 of the Programming register (see section
8.2.2). Figure 18 shows typical transmit waveforms.
I2S
SCLK
b15
b0
b15
b0
SDO
FSO
Figure 18 I2S Mode Support
6.5 Device Control
The CMX7131/CMX7141 can be set into the relevant mode to suit its environment. These modes are
described in the following sections and are programmed over the C-BUS: either directly to operational
registers or, for parameters that are not likely to change during operation, via the Programming register
($C8).
For basic operation:
(1) enable the relevant hardware sections via the Power Down Control register
(2) set the appropriate mode registers to the desired state
(3) select the required Signal Routing and Gain
(4) use the Modem Control register to place the device into Rx or Tx mode
To conserve power when the device is not actively processing a signal, place the device into IDLE mode.
Additional power savings can be achieved by disabling any unused hardware blocks but care must be
taken not to disturb any sections that are automatically controlled. Note that the BIAS block must be
enabled to allow any of the input or output blocks to function.
See:
o
o
o
Power Down Control - $C0 write
Modem Control - $C1 write
Modem Configuration - $C7 write.
2014 CML Microsystems Plc
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