HT98R068-1 Two-way Radio OTP MCU
Sub-tone Function
For the open systems such as walkie-talkies, under conditions of limited frequency
channels, a sub-tone method can be applied to increase the same frequency channel
numbers and to receive the required signals. Users at the receiving port should select the
correct sub-tone type and channel so as to decode the data properly and reduce
unnecessary signals. This will help to reduce the problems of mutual interference and
frequency bands. The device provides two main sub-tone options described as follows.
CTCSS Setting
This produces analog signals of sinusoidal frequency from 62.5Hz~254.1Hz and contains
51 groups of standard channel selections which meet the relevant specifications. An
additional user-defined channel is provided to increase the flexibility of data protection.
The channel is selected by using I/O CMD-2Bh sharing with DCS. For the audio
processor, there are still two registers in which data changes should be noted when being
used. In the Rx mode, it is acceptable to use polling (I/O CMD-23h [3]) or interrupt (10008
I/O CMD-23h [3]) methods to detect whether it is the same as the setup channel. The
table below provides relevant table and design descriptions.
Tone
number
CTCSS
freq.(Hz)
Tone
number
CTCSS
freq.(Hz)
Tone
number
CTCSS
freq.(Hz)
01h 67 12h 123 23h
225.7
02h 71.9 13h 127.3 24h
233.6
03h 74.4 14h 131.8 25h
241.8
04h 77 15h 136.5 26h
250.3
05h 79.7 16h 141.3 27h 69.3
06h 82.5 17h 146.2 28h 62.5
07h 85.4 18h 151.4 29h
159.8
08h 88.5 19h 156.7 2Ah
165.5
09h 91.5 1Ah 162.2 2Bh
171.3
0Ah 94.8 1Bh 167.9 2Ch
177.3
0Bh 97.4 1Ch 173.8 2Dh
183.5
0Ch 100 1Dh 179.9 2Eh
189.9
0Dh 103.5 1Eh 186.2 2Fh 196.6
0Eh 107.2 1Fh 192.8 30h 199.5
0Fh 110.9 20h 203.5 31h
206.5
10h 114.8 21h 210.7 32h
229.1
11h 118.8 22h 218.1 33h
254.1
CTCSS
Frequency and Tone Numbers Table
The device supports coded mark inversion designing of 180° and 120°. The Tx mode is
controlled by the I/O CMD-31h [0] bit. It will generate a reversion signal by 1
0 or 0
1.
The Rx mode detection is selected by the I/O CMD-31h [1] bit. If detecting a phase
chaing, the I/O CMD-30h [0] bit will change to 1{note: this bit must clear to 0 automatically
(see the Audio Processor Status Reset section)}. And the interrupt SPI data is sharing
with (it is 10008h too). Hence, when using the CTCSS anti-tone detection function, you
must check the I/O CMD-23h [3] and I/O CMD-30h [0] bits. The table below provides
relevant table and design descriptions.
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