CTCSS Signalling Processor
FX818
SUB-AUDIO CONTROL Register (Hex address $80)
This register is used to control the functions of the device as described below:
CTCSS TX ENABLE
and DECODER
ENABLE
These two bits enable and disable the CTCSS decoder (Rx) or transmitter (Tx)
according to the table below:
(Bits 7 and 6)
Tx
Bit 7
0
0
1
1
Rx
Bit 6
0
1
0
1
Function
Tx disabled, Rx disabled
Tx disabled, Rx enabled
Tx enabled, Rx disabled
Tx enabled, Rx enabled
CTCSS FAST
DETECT ENABLE
(Bit 5)
When this bit is "1", the "FAST CTCSS DETECT" or "FAST CTCSS
PREDICTIVE" mode is enabled, depending upon the setting of FAST CTCSS
MODE (Bit 3 SUB-AUDIO SET-UP Register, $82). When this bit is "0", both
"FAST CTCSS DETECT" and "FAST CTCSS PREDICTIVE" tone detectors are
disabled.
(Bits 4, 3, 2, 1 and 0)
Reserved for future use. These bits should be set to "0".
SUB-AUDIO SET-UP Register (Hex address $82)
This register is used to define the CTCSS parameters, as described below:
CTCSS DECODER
BANDWIDTH
These four bits set the bandwidth of the CTCSS tone decoder according to
the table below:
(Bits 7, 6, 5 and 4)
BANDWIDTH
Bit 7
Bit 6
Bit 5
Bit 4
Will Decode
Will Not Decode
±2.4%
1
1
1
1
1
1
1
1
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
±1.1%
±1.3%
±1.6%
±1.8%
±2.0%
±2.2%
±2.5%
±2.7%
±2.7%
±2.9%
±3.2%
±3.5%
±3.7%
±4.0%
±4.2%
FAST CTCSS MODE
(Bit 3)
When CTCSS FAST DETECT ENABLE (Bit 5 SUB-AUDIO CONTROL Register,
$80) is "1", this bit selects the "FAST CTCSS DETECT" or the "FAST CTCSS
PREDICTIVE" mode, according to the table below:
ã 1997 Consumer Microcircuits Limited
9
D/818/4
CMLMICRO [ CML MICROCIRCUITS ]
