Digital PMR Radio Processor
CMX7131/CMX7141
6.5.1 General Notes
In normal operation, the most significant registers, in addition to the TxData and RxData blocks, are:
o
o
o
o
o
o
Modem Control - $C1 write
IRQ Status - $C6 read
Analogue Output Gain - $B0 write
Input Gain and Signal Routing - $B1 write
TxAuxData Write - $C2 write
Vocoder Analogue Gain- $C3 write
Setting the Modem Mode to either Rx or Tx will automatically increase the internal clock speed to its
operational speed and bring the device out of its powersave mode, whilst setting the Modem Mode to Idle
will automatically return the internal clock to a lower (powersaving) speed. To access the Program Blocks
(through the Programming register, $C8) the device MUST be in Idle mode.
Under normal circumstances the CMX7131/CMX7141 manages the main clock control automatically,
using the default values loaded in Program Block 3.
6.5.2 Interrupt Operation
The CMX7131/CMX7141 will issue an interrupt on the IRQN line when the IRQ bit (bit 15) of the Status
register and the IRQ Mask bit (bit 15) of the Interrupt Mask register are both set to 1. The IRQ bit is set
when the state of the interrupt flag bits in the Status register change from a 0 to 1 and the corresponding
mask bit(s) in the Interrupt Mask register is (are) set. Enabling an interrupt by setting a mask bit (01)
after the corresponding Status register bit has already been set to 1 will also cause the IRQ bit to be set.
All interrupt flag bits in the Status register, except the PRG flag (bit 0), are cleared and the interrupt
request is cleared following the command/address phase of a C-BUS read of the Status register. The
PRG flag bit is set to 1 only when it is permissible to write a new word to the Programming register.
See:
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IRQ Status - $C6 read
Interrupt Mask - $CE write
Continuous polling of the Status register ($C6) is not recommended due to both the increase in response
time, host loading and potential digital noise generation due to bus activity. If the host cannot support a
fully IRQ driven interface then it should route the IRQ signal to a host I/O pin and poll this pin instead.
6.5.3 Signal Routing
The CMX7131/CMX7141 offers a flexible routing architecture, with three signal inputs, a choice of two
modulator configurations (to suit 2-point modulation or I/Q schemes) and a single audio output.
See:
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o
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Input Gain and Signal Routing - $B1 write
Modem Control - $C1 write
Modem Configuration - $C7 write
The analogue gain/attenuation of each input and output can be set individually, with additional Fine
Attenuation control available via the Program Blocks in the CMX7131/CMX7141. The Mic and Speaker
gains are set by the vocoder. If the SPI-Codec mode is used, additional level control is available using the
$B0 and $B1 registers.
See:
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o
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Analogue Output Gain - $B0 write (Tx MOD1 and 2, Rx AUDIO)
Input Gain and Signal Routing - $B1 write (Rx DISC input, Tx MIC, MOD1 and 2)
Vocoder Analogue Gain- $C3 write (Rx SPI/PCM Voice level).
2014 CML Microsystems Plc
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