AX.25 Modem
CMX7031/CMX7041
7.4
Device Control
The CMX7031/CMX7041 should be configured to the mode that suits the environment in which it is to be
used. 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 (Data rate, DTMF Tone etc.)
3. Select the required Signal Routing and Gain
4. Use the Mode Control register to place the device into Rx or Tx mode.
To conserve power when the device is not actively processing an analogue signal, place the device into
Idle mode. Additional powersaving can be achieved by disabling the unused hardware blocks, however,
care must be taken not to disturb any sections that are automatically controlled.
See:
o
o
o
o
Power Down Control - $C0 write
Mode Control – $C1 write
Output Level – $C2 write
Input Gain and Routing - $B1 write
7.4.1 Signal Routing
The CMX7031/CMX7041 offers a flexible routing architecture, with three signal inputs, and a selection of
two modulator outputs (to suit two-point modulation schemes). The signal processing blocks can be
routed to any of the three input signal pins via Input 1 block. The outputs from signal processing blocks are
determined by the settings of the Input Gain And Routing register in Tx mode.
See:
o
o
Input Gain and Routing - $B1 write
Mode Control – $C1 write
The analogue gain/attenuation of each input and output can be set individually.
See:
o
o
o
Output Level – $C2 write
Input Gain and Routing - $B1 write
GPIO Control - $A7 16-bit write
7.4.2 Mode Control
The CMX7031/CMX7041 operates in one of three modes:
o
o
o
Idle
Rx
Tx
At power-on or following a Reset, the device will automatically enter Idle mode, which allows for the
maximum powersaving whilst still retaining the capability of monitoring the AuxADC inputs (if enabled). It is
only possible to write to the Programming register whilst in Idle mode.
See:
o
Mode Control – $C1 write
7.5
Transmitting DTMF Tones
The DTMF signals to be generated are loaded into b4-0 of the TxData1 register ($B6) from the host
whenever the device is in DTMF Tx mode. Setting b5 will generate a “Null” tone. Table 3 shows the DTMF
tone pairs,
2013 CML Microsystems Plc
Page 21
D/7031/7041_FI-4.x/5
CMLMICRO [ CML MICROCIRCUITS ]
