Evaluation Kit for CMX838 Family Radio Processor
18
EV8380 User Manual
5.2.3.1 Set the Audio Tone Frequency
To program the CMX838 to generate a user-defined audio tone the user must first compute the “argument
data” according to the following formula:
6 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 10 (program audio frequency ringing tone).
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 transmit a 620Hz tone, the required C-BUS sequence would be
1. Write $0986 to 16 BIT SUBAUDIO TASK DATA register ($8E).
2. Write $4A to SUBAUDIO PROCESSOR GENERAL CONTROL ($93) register.
5.2.3.2 Internally Connect the AUX I/O Pin to the Audio Tone Generator
To internally connect the audio tone generator output to the AUX I/O pin, argument data for the AUX I/O pin
configuration must be loaded into the argument register, and task 14 (configure aux pin as output) should
then be sent to the tone signaling processor.
The argument data for AUX I/O pin configuration has the following format in the SUBAUDIO TASK DATA
($95) register:
Bit 7
Bit 6-3
Bit 2-0 (These bits are Don’t Care if Bit 7 is a logic 0)
Bit 2 Bit 1 Bit 0 AUX I/O pin output signal
1=enable aux
pin as output
1
1
1
1
0
0
1
1
0
1
0
1
RX Decode Status bit
Audio Tone
Don’t care
0=enable aux
pin as input
Output logic 0
Output logic 1
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 have the CMX838 produce a 620Hz ringing tone and present the tone on the AUX I/O pin, set
up the audio tone with task 10 and then enable the AUX I/O pin output with task 14.
1.
2.
3.
4.
5.
Write $0986 to 16 BIT SUBAUDIO TASK DATA ($8E) register.
Write $4A to SUBAUDIO PROCESSOR GENERAL CONTROL ($93) register.
Wait 250µs.
Write $85 to SUBAUDIO TASK DATA ($95) register.
Write $4E to SUBAUDIO PROCESSOR GENERAL CONTROL ($93) register.
If the CMX838 is already in the Tx mode, the newly programmed tone will immediately begin to be
transmitted.
Note that once the audio tone generator is enabled, the frequency can be changed by reissuing task 10.
5.2.4 How to Detect a Standard CTCSS Tone
To program the CMX838 to detect a standard (TIA-603) CTCSS tone, the user must first load the argument
data corresponding to the tone of interest into the argument data register, then issue task 4 (enable/disable
tone detector) to the tone signaling processor. (NOTE: These steps can be repeated as needed to configure
a “tone watch list” but a special mode can be used to quickly enable/disable multiple detectors; see section
5.2.5 for more information.)
¤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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