SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
MITSUBISHI MICROCOMPUTERS
3826 Group
41
CTCSS Function
(Continuous Tone-Controlled Squelch System)
The CTCSS function is used to generate the sine wave of single
frequency automatically. The CTCSS output waveform can be out-
put using DA2 function. CTCSS waveform is outputted by setting
“1” to the CTCSS/DA2 output enable bit (bit 1 of address 003616),
and setting “1” to the CTCSS/DA2 selection bit (bit 3 of address
003616). In order to set the frequency of CTCSS output, value is
written in the CTCSS timer. The CTCSS timer consists of a 10-bit
timer. When writing a value to the CTCSS timer, write the low-or-
der byte first.
Rating frequency (Hz)
67.0
77.0
88.5
100.0
107.2
114.8
123.0
131.8
141.3
151.4
162.2
173.8
186.2
203.5
218.1
233.6
250.3
n (Timer value)
465
405
352
312
291
271
253
236
220
205
192
179
167
153
142
133
124
Error frequency (Hz)
0.06
–0.03
0.027
–0.16
–0.18
0.09
0.03
0.06
0.10
0.30
–0.28
–0.19
–0.58
0.43
–0.39
–0.30
Deviation (%)
0.089
–0.038
0.030
–0.160
–0.167
0.078
0.026
0.043
0.073
0.198
–0.174
–0.109
–0.101
–0.284
0.198
–0.167
–0.120
Output frequency (Hz)]
67.06
76.97
88.53
99.84
107.02
114.89
123.03
131.86
141.40
151.70
161.92
173.61
186.01
202.92
218.53
233.20
250.00
Table 11 Example of frequency accuracy (at f(XIN) = 4 MHz)
VCC
2
f =
(Hz)
f (XIN)/2
(n+1) 64
When reading a value from the CTCSS timer, read the high-order
byte first. By the value n written in the CTCSS timer, the sine wave
of the following frequency is generated.
Set “00616” or more to the CTCSS timer. “0016” is automatically
set to the high-order of the CTCSS timer and “0616” is automati-
cally set to the low-order of the CTCSS timer after reset release.
The amplitude of CTCSS output is obtained by the following for-
mula.
C =
If the D-A2 conversion register is read when the CTCSS function
is selected, the digital value of CTCSS output can be read.