CTCSS Signalling Processor
FX818
8-bit Read Only Registers
HEX
ADDRESS/
COMMAND
REGISTER
NAME
BIT 7
(D7)
BIT 6
BIT 5
(D5)
BIT 4
(D4)
BIT 3
(D3)
BIT 2
(D2)
CTCSS RX TONE
BIT 1
(D1)
BIT 0
(D0)
(D6)
CTCSS
FAST
$81
SUB-AUDIO
STATUS
0
0
TONE
DECODE
MSB
BIT 3
CTCSS
IRQ
LSB
BIT 0
TONE
BIT 2
CTCSS FAST
IRQ
BIT 1
GP TIMER
IRQ
$8F
IRQ FLAG
0
0
0
0
0
FLAG
FLAG
FLAG
Read Only Register Description
SUB-AUDIO STATUS Register (Hex address $81)
This register is used to indicate the status of the device as described below:
(Bit 7)
Reserved for future use. This will be set to "0" but should be ignored by user's
software.
CTCSS FAST TONE
(Bit 6)
When Bit 5 in the SUB-AUDIO CONTROL Register and Bit 3 in the SUB-AUDIO
SET-UP Register are set to enable FAST CTCSS DETECT mode, this bit will be
set to "1" if a periodic tone is detected. If no periodic tone is detected this bit will
be "0".
When bits 5 and 3 are set to enable FAST CTCSS PREDICTIVE mode, this bit
will be set to "1" if a periodic tone that matches the frequency programmed in the
CTCSS TX/FAST RX Register is detected. If no match is found this bit will be
"0".
When Bit 5 in the SUB-AUDIO CONTROL Register is set to "0" this bit will be
"0".
(Bit 5)
Reserved for future use. This will be set to "0" but should be ignored by the
user's software.
TONE DECODE
(Bits 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 means that a tone has been decoded and its characteristics are
defined by the bandwidth (See SUB-AUDIO SET-UP Register bits 7, 6, 5 and 4)
and the CTCSS RX TONE number (See SUB-AUDIO STATUS Register bits 3,
2, 1 and 0).
When Bit 6 in the SUB-AUDIO CONTROL Register is set to "0" the TONE
DECODE bit 4 will be set to "0".
Identification of a valid tone which is not in the pre-programmed list of up to 15
tones will cause the decoder to move to the TONE DECODE state with the RX
TONE address of "1111" in bits 3, 2, 1 and 0; indicting 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 timeout period, then the decoder will move to
NOTONE state and the identification of pre-programmed tones will start again.
ã 1997 Consumer Microcircuits Limited
14
D/818/4
CMLMICRO [ CML MICROCIRCUITS ]
