Evaluation Kit for CMX838 Family Radio Processor
17
EV8380 User Manual
5.2
Tone Signaling Processor Examples
NOTE that before any tasks can be issued to the tone signaling processor, the baseband clocks must first be
setup properly and running.
5.2.1 How to Generate a Standard CTCSS Tone
To select a pre-programmed subaudio tone, the user must first load the tone index (i.e. argument data) into
the argument data register and then issue task # 8 (select subaudio tone from pre-programmed list) to the
tone signaling processor.
NOTE: To determine the value to load in the SUBAUDIO PROCESSOR GENERAL CONTROL ($93) register,
the power control and IRQ control bits should be logically “OR-ed” with the desired task field.
For example, to set up the CMX838 to transmit an 114.8Hz tone (standard CTCSS tone), the required C-BUS
sequence would be:
1. Write $11 to SUBAUDIO TASK DATA ($95) register.
2. Write $48 to SUBAUDIO PROCESSOR GENERAL CONTROL ($93) register.
5.2.2 How to Generate A User-Defined TX Subaudio Tone
To program the CMX838 to generate a user-defined subaudio tone, the user must first calculate the argument
data according to the following formula:
36 65536 f
§
·
¸
¹
Argument = INT 0.5 +
¨
100000
©
where f is the tone to be transmitted. Load the binary equivalent of the argument data into 16 BIT SUBAUDIO
TASK DATA register ($8E), then issue task 9 (program user-defined subaudio tone) to the tone signaling
processor.
NOTE: To determine the value to load in the SUBAUDIO PROCESSOR GENERAL CONTROL ($93) register,
the power control and IRQ control bits should be logically “OR-ed” with the desired task field.
For example, to set up the processor to generate a 65 Hz tone, the required C-BUS sequence would be
1.
2.
Write $05FE to 16 BIT SUBAUDIO TASK DATA register ($8E).
Write $49 to SUBAUDIO PROCESSOR GENERAL CONTROL ($93) register.
5.2.3 How to Generate an Audio Tone at the AUX I/O Pin
The CMX838 audio tone generator produces ringing/alert square wave tones at user defined frequencies. It
can also filter those audio signals to make them more sinusoidal.
To use a generated audio tone signal the AUX I/O pin must be configured to internally connect to the audio
tone generator output. (When the AUX I/O pin is configured in this manner, external connections to the
AUX I/O pin may load and affect the audio tone generator output.)
If desired, the AUX I/O pin may also be internally switched to drive the CMX838 audio processing path to filter
and pass an audio tone to both loudspeaker and TXMOD1 and TXMOD2 output pins. This allows the
CMX838 to internally generate an audio tone and internally connect it to the audio processing path, using the
AUX I/O pin to do so. If desired, the generated audio tone may be driven off-chip via the AUX I/O pin without
also internally connecting it to the CMX838 audio processing path.
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Doc. # 20480230.001
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