Family Radio CTCSS 'Type 2' Encoder and Decoder
CMX808A
TONE CLONING Register (Hex address $9C)
This register enables and disables tone cloning as shown below:
$9C = $01 enables tone cloning.
$9C = $00 disables tone cloning.
Figure 4 shows the tone cloning routine.
8-bit Read Only Registers
HEX
ADDRESS/
COMMAND
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)
CTCSS RX TONE
BIT 1
$81
SUB-AUDIO
STATUS
0
0
0
0
TONE
DECODE
MSB
BIT 2
LSB
BIT 0
Read Only Register Description
SUB-AUDIO STATUS Register (Hex address $81)
Reading the SUB-AUDIO STATUS register clears the interrupt (IRQN).
This register is used to indicate the status of the device as described below:
Reserved for future use. These will be set to "0" but should be ignored by user's
software.
(Bits 7, 6, 5 and 4)
This bit indicates the status of the tone decoder. A "1" indicates a tone has been
detected (TONE DECODE) and a "0" indicates the loss of the tone (NOTONE).
TONE DECODE
(Bit 3)
TONE DECODE means that a tone has been decoded and its characteristics are
defined by the bandwidth (see SUB-AUDIO CONTROL register $80, Bits 5, 4, 3
and 2) and the CTCSS RX TONE number (see SUB-AUDIO STATUS register
$81, Bits 2, 1 and 0).
When Bit 6 in the SUB-AUDIO CONTROL register $80 is set to "0" the TONE
DECODE Bit 3 will be set to "0".
Identification of a valid tone which is not in the pre-programmed list of up to 7
tones will cause the decoder to move to the TONE DECODE state with the RX
TONE address of "111" in Bits 2, 1 and 0; indicating a valid but unrecognised
tone. Loss of tone will cause the NOTONE timer to be started. If loss of tone
continues for the duration of the time-out period, then the decoder will move to
NOTONE state and the identification of pre-programmed tones will start again.
The time-out period is not user adjustable.
These three bits hold a Hex number. Numbers $0 to $6 represent the address
of the CTCSS tone decoded according to the tones programmed in the CTCSS
RX PROGRAM register $84. The Hex number $7 indicates the presence of any
tone that is not described by CTCSS DECODER BANDWIDTH (Bits 5, 4, 3 and
2 in the SUB-AUDIO CONTROL register $80) and CTCSS FREQUENCY (Bits
11 to 0 in the CTCSS RX PROGRAM register $84).
CTCSS RX TONE
(Bits 2, 1 and 0)
2003 CML Microsystems Plc
11
D/808A/6
CMLMICRO [ CML MICROCIRCUITS ]
