FX818 datasheet(9/26 Pages) CMLMICRO

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CTCSS Signalling Processor

FX818

D/818/4

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

(Bits 7 and 6)

These two bits enable and disable the CTCSS decoder (Rx) or transmitter (Tx)

according to the table below:

Bit 7

Bit 6

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

(Bits 7, 6, 5 and 4)

These four bits set the bandwidth of the CTCSS tone decoder according to

the table below:

BANDWIDTH

Bit 7

Bit 6

Bit 5

Bit 4

Will Decode

Will Not Decode

±1.1%

±2.4%

±1.3%

±2.7%

±1.6%

±2.9%

±1.8%

±3.2%

±2.0%

±3.5%

±2.2%

±3.7%

±2.5%

±4.0%

±2.7%

±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:

FX818 Datasheet(PDF) 9 Page - CML Microcircuits

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