Family Radio CTCSS 'Type 2' Encoder and Decoder
CMX808A
1.5
General Description
The CMX808A is a programmable CTCSS ‘Type 2’ encoder and decoder for Family Radio, see Figure 1.
The receiver of the CMX808A decodes a user-programmable set of up to 7 tones with minimum software
intervention; the band-pass filter is designed to filter out the CTCSS sub-audio tones. A high resolution
tone encoder performs accurate generation of CTCSS tones.
Each function, and the routing of signals, is flexible and may be configured or controlled by the user's
software.
1.5.1
Software Description
Address/Commands
Instructions and data are transferred, via "C-BUS", in accordance with the timing information given
in Figure 6.
Instruction and data transactions to and from the CMX808A consist of an Address/Command
(A/C) byte which may be followed by either:
(i)
(ii)
8-bit Write Only Registers
HEX
ADDRESS/
COMMAND
$01
REGISTER
NAME
BIT 7
(D7)
BIT 6
(D6)
BIT 5
(D5)
BIT 4
(D4)
BIT 3
(D3)
BIT 2
(D2)
BIT 1
(D1)
BIT 0
(D0)
a further instruction or data (1 or 2 bytes) or
a status or Rx data reply (1 byte)
GENERAL
RESET
SUB-AUDIO
CONTROL
AUDIO
CONTROL
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
CTCSS
IRQ
MASK
LSB
BIT 0
$80
CTCSS
TX
DECODER
ENABLE
ENABLE
TX BPF
ENABLE
RX BPF
ENABLE
$82
CTCSS DECODER BANDWIDTH
MSB
LSB
0
BIT 3
BIT 2
BIT 1
BIT 0
AUDIO ATTENUATION
BPF
MSB
UN-MUTE
BIT 4
BIT 3
BIT 2
BIT 1
16-bit Write Only Registers
HEX
ADDRESS/
COMMAND
REGISTER
NAME
CTCSS
TX FREQ.
(Byte 1)
CTCSS
TX FREQ.
(Byte 2)
CTCSS RX
PROGRAM
(Byte 1)
CTCSS RX
PROGRAM
(Byte 2)
BIT 7
(D7)
CTCSS
TX
NOTONE
BIT 6
(D6)
BIT 5
(D5)
BIT 4
(D4)
BIT 3
(D3)
BIT 2
(D2)
BIT 1
(D1)
BIT 0
(D0)
CTCSS TX FREQUENCY
0
0
MSB
BIT 12
BIT 11
CTCSS TX FREQUENCY
BIT 10
BIT 9
BIT 8
LSB
BIT 0
$83
BIT 7
0
$84
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
CTCSS TONE ADDRESS
CTCSS FREQUENCY
MSB
LSB
MSB
BIT2
BIT 1
BIT 0
BIT 11
BIT 10
BIT 9
CTCSS FREQUENCY
BIT6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 8
LSB
BIT 0
BIT 7
2003 CML Microsystems Plc
7
D/808A/6
CMLMICRO [ CML MICROCIRCUITS ]
