EM78P568

8-bit OTP Micro-controller

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* This specification are subject to be changed without notice.

46

01/31/2004

V4.7

(3) TX : transmitting audio

Audio

BPF

VRF

VRF

Rx AMP

MIC AMP

Z C

AURX/P65

RXO

RXI

MICI

MICO

Summing

MTX/P66

VRF

-10dB

0dB

ASW1 = 1

ASW2 = 1

RXPWR

LPFPWR

BPFPWR = 1

Sub-Audio

LPF

ASW4

MUX

PORT66

MTX

MUX

PORT65

AURX

P65S

P66S = 1

AMP

MUX

ASW3

MUX

MUX

MUX

DETO

TXPWR = 1

TXPWR = 1

RXPWR

VRX1

VTX1

VRX2

VTX2

VRX3

VTX3

VRX4

VTX4

(from DAC output buffer B2)

CTCSS tone input

MUX

MICO

AMUTE = 0

Fig.20

(4) TX : transmitting CTCSS tone

Audio

BPF

VRF

VRF

Rx AMP

MIC AMP

Z C

AURX/P65

RXO

RXI

MICI

MICO

Summing

VRF

-10dB

0dB

ASW1

ASW2

RXPWR

LPFPWR = 1

BPFPWR

Sub-Audio

LPF

ASW4 = 1

MUX

PORT66

MTX

MUX

PORT65

AURX

P65S

P66S = 1

AMP

MUX

ASW3 = 1

MUX

MUX

MUX

DETO

TXPWR

TXPWR = 1

RXPWR

VRX1

VTX1

VRX2

VTX2

VRX3

VTX3

VRX4

VTX4

(from DAC output buffer B2)

CTCSS tone input

MUX

MICO

AMUTE

MTX/P66

Fig.21

VII.10.2 Special application on Audio/CTCSS tone mixing output

Generally speaking, users can use built-in DAC tone gen.(described in VII.9) to generate CTCSS

tone accompanied with audio on MTX/P66 pin output without problem. For some customers, due to

modulation index criteria of their FM modulator cannot accept built-in CTCSS tone because this level is

too large for them to use.

In this case, there are two ways to solve this problem :

(1) One way is not to use built-in DAC tone gen. but need to program built-in DAC to generate CTCSS

tone by user software algorithm. User software algorithm can normalize the final CTCSS tone level

to their requirement without adding any external elements.