CTCSS Signalling Processor

FX818

© 1997 Consumer Microcircuits Limited

10

D/818/4

DETECT/

PREDICTIVE

Bit 3

Function

0

DETECT mode

1

PREDICTIVE mode

If the CTCSS FAST DETECT ENABLE bit is "0" then both modes are

deselected.

(Bits 2, 1 and 0)

Reserved for future use. These should be set to "0".

GENERAL CONTROL Register (Hex address $88)

This register is used to control the functions of the device as described below:

BPF ENABLE

(Bit 7)

When this bit is "1" the audio band-pass filter is enabled. When this bit is "0" the

audio band-pass filter is disabled (powersaved).

BPF UN-MUTE

(Bit 6)

When this bit is "1" the audio band-pass filter output is switched to the RX

AUDIO OUT pin. When this bit is "0" the output of the filter is disconnected from

RX AUDIO OUT, which is then in a high impedance state.

This control, along with BPF ENABLE, allows the filter to power up and settle

internally before switching the output on, to avoid clicks when coming out of

powersave.

BPF 6dB PAD

(Bit 5)

When this bit is "1" a 6dB attenuator is inserted into the output of the audio

band-pass filter. When this bit is "0" the output of the audio band-pass filter is

not attenuated.

(Bits 4, 3 and 2)

Reserved for future use. These should be set to "0".

TIMER ENABLE

(Bit 1)

When this bit goes to a "1" the general purpose timer is restarted and its internal

register is re-loaded from the value specified in the GENERAL PURPOSE

TIMER Register (Hex address $8B). It will then count down from the count held

in its internal register. When this bit is "0" the count down is disabled and the

last pre-programmed value is retained in the timer's internal register.

TIMER RE-CYCLE

(Bit 0)

When this bit is "1" the general purpose timer will re-load its internal register from

the value specified in the GENERAL PURPOSE TIMER Register (Hex Address

$8B) when the count in the internal register reaches zero (i.e. the timeout has

expired). It then restarts the count down, so that the timer continuously cycles.

When this bit is "0" the general purpose timer will stop when the count in the

internal register reaches zero (i.e. the timeout has expired). The timer can only

be restarted by reloading a value into the GENERAL PURPOSE TIMER Register

(Hex address $8B).

If this bit is switched from "1" to "0" whilst the timer is enabled then the timer will

complete the present count before stopping.