Evaluation Kit for CMX838 Family Radio Processor
12
EV8380 User Manual
4.1.2.2 Operating the CMX838 from a System Clock
To operate the CMX838 from a system clock signal e.g. a host microcontroller’s clock:
1) Please consult the CMX838 data bulletin for appropriate system clock frequency choices.
2) Ensure jumpers E1 and E2 are removed.
3) Connect the system clock signal to the XTALIN pin of the CMX838 by way the jumper E1 pins.
a. Please consult the CMX838 data bulletin for recommendations on drive level.
4) Write a byte to the SYNTHESIZER BASEBAND CLOCK CONTROL ($89) register to configure the
CMX838 clock generation circuits.
a. For example, if the system clock operates at 4.0MHz, a byte of $40 will enable baseband clock
generation from the 4.0MHz system clock signal.
4.2
Subaudio Processing
The CMX838 offers tremendous flexibility in the ability to process subaudio tones:
1) Single tone generation (standard and user-defined CTCSS tones)
2) Single tone detection (standard and user-defined CTCSS tones)
3) For tone detection, the formation of a tone ‘watch list’ is possible, with the list comprised of as many as
50 different standard and non-standard CTCSS tones that are effectively detected in parallel.
4) Multiple tone detection; the CMX838 can be configured to search for all of the standard CTCSS tones
and/or a user programmed tone.
5) Custom tone detection: one of the CMX838 parallel CTCSS tone decoders is programmable and
allows configuration of an arbitrary tone
Flexibility is also offered by way of adjustable filter settings and gain stages in the CMX838 subaudio signal
path.
The CMX838 supports individual enabling/disabling of tones to allow users to configure their own tone sets
with each enabled tone effectively detected in parallel with all other enabled tones. The CMX838 also offers
two pre-configured sets of CTCSS tones so a full set may be activated in one step. One set includes all 39
TIA-603-A tones. The second set includes 50 commonly encountered CTCSS tones (including all 39 tones
specified in the TIA-603-A standard).
Once activated, a pre-configured tone set may be edited. For example, the set may be configured to enable
all 39 TIA-603-A tones in one step and subsequently edited to remove or add more tones.
In general, to generate or detect one of these tones, the hex value for the tone of interest should be loaded
into the SUBAUDIO TASK 8 BIT DATA ($95) register. In typical applications, once the tone signaling
processor is initialized, its primary behavior (CTCSS encode and decode) is steered by the TX/RX bit of the
SETUP Register ($80) so tone sets do not have to be repeatedly configured.
¤2001 MX-COM, Inc.
4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA
www.mxcom.com tel: 800 638 5577 336 744 5050 fax: 336 744 5054
Doc. # 20480230.001
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