CMX838D1 View Datasheet(PDF) - CML Microsystems Plc

Part Name

Description

MFG CO.

CMX838D1

FRS/PMR446/GMRS Family Radio Processor

CML Microsystems Plc 

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FRS/PMR446/GMRS Family Radio Processor

CMX838

5.1.2.3 AUDIO CONTROL Register ($81)

PRE-

EMPHASIS/LPF

CONTROL

(PRE LPF CTRL)

Bit 7 and Bit 6

The first stage of filtering following Input Mux 1 can be configured as a 2nd order low-

pass filter, as a pre-emphasis network or bypassed. Reference Figure 3.

Bit 7

0

0

1

1

Bit 6

0

1

0

1

Result

Pre-emphasis

Low-pass filter

Mute, output is held to VDD/2

bypass

HIGHPASS

FILTER BYPASS

Bit 5

Audio Level

Bit 4,3,2,1,0

When this bit is a Logic ‘1’ the high-pass audio filter is bypassed. Reference Figure 3.

The five least significant bits in this register are used to set the gain/attenuation of the

audio level control as shown in the table below. This digitally controlled amplifier is

located in the audio path between the input low-pass filter/pre-emphasis network and

the 6th order high-pass filter. Its primary purpose is to trim the nominal audio level such

that the dynamic range is maximized.

43210

00000

00001

00010

00011

00100

00101

00110

00111

01000

01001

01010

01011

01100

01101

01110

01111

10000

10001

10010

10011

10100

10101

10110

10111

11000

11001

11010

11011

11100

11101

11110

11111

AUDIO GAIN

Off

-7.5dB

-7.0dB

-6.5dB

-6.0dB

-5.5dB

-5.0dB

-4.5dB

-4.0dB

-3.5dB

-3.0dB

-2.5dB

-2.0dB

-1.5dB

-1.0dB

-0.5dB

0.0dB

0.5dB

1.0dB

1.5dB

2.0dB

2.5dB

3.0dB

3.5dB

4.0dB

4.5dB

5.0dB

5.5dB

6.0dB

6.5dB

7.0dB

7.5dB

 2003 CML Microsystems Plc

Table 7: AUDIO CONTROL Register ($81)

32

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