CMX838 View Datasheet(PDF) - CML Microsystems Plc
Part Name
Description
MFG CO.
'CMX838' PDF : 71 Pages View PDF
FRS/PMR446/GMRS Family Radio Processor
CMX838
4.2.4.3 RX Configuration
The following four tasks are used to control the decode behavior.
4.2.4.3.1 Enable or Disable Tone Detector (Task 4)
This task can be used to enable or disable tone detectors 1 to 51. Tone Detectors 1 to 50 have preset
detection center frequencies while tone detector 51 has a user programmable center frequency. This task
may be issued multiple times to configure a tone watch list. It is recommended not to include non TIA-603
tones with their adjacent TIA tones in a watch list.
Load argument in register $95, then issue task 4. Repeat as needed to configure tone watch list.
The argument data has the following format in the 8 bit task data register ($95).
Bit 7
1=enable
0=disable
Bit 6
Don’t
care
Bits 5-0
Tone detector index number (1-51)
Additionally using index 63 can enable or disable all detectors while issuing just
one task. Enabling index 62 enables detection of all TIA-603 Tones. There is no
single command to disable just the TIA-603 Tone Detectors – instead use index 63
to disable all detectors.
For example to enable the 67Hz Tone Detector:
$95 0x81
$93 0x64
// data to enable tone index 1 (67Hz)
// task command to actually enable tone detector (and IRQ’s)
4.2.4.3.2 Program User Defined RX Sub-Audio Tone (Task 5)
This task is used to program the center frequency of user programmable detector 51. Load the Argument
value in register $8E, then issue task 5.
The argument can be calculated according to the following equations.
N = INT 96 ⋅ 511⋅ f
100000
R
=
INT
0.5
+
511 −
100000 ⋅
96 ⋅ f
N
Argument = N ⋅ 64 + R
The argument data for 65 Hz would be 31*64+14 = 0x07CE
The programmed center frequency can be back calculated by:
f
=
100000 ⋅ N
96(511− R)
In the example above the actual center frequency would be 64.97 Hz.
A C-BUS sequence to setup tone detector 51 for 65Hz and enable just it would be:
$8E 0x07CE
$93 0x45
// Argument data for user defined 65Hz RX Tone.
// Task 5 command (No IRQ’s enabled)
wait 250µs
$95 0x3F
$93 0x44
// Task 4 argument data to disable all decoders
// Task 4 command (No IRQ’s enabled)
wait 250µs
$95 0xB3
$93 0x64
// Task 4 argument data to enable decoder 51 (The user definable one)
// Task 4 command (with IRQ’s enabled)
wait 250µs
$93 0x60
// Task 0 command (to place device normal run mode with IRQ’s enabled)
// last command is not required if the device was already in normal run mode
2003 CML Microsystems Plc
22
D/838/8
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