EM78P568

8-bit OTP Micro-controller

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* This specification are subject to be changed without notice.

43

01/31/2004

V4.7

(1) DAC program mode：

The below item “1” is for DAC general mode. The below item “2,3” are for DAC tone generator mode.

1. DAT/DAD = 0

DAC general mode, software-program DAC from DA7 ~ DA0 register bits , disable DAC

tone generator。

2. DAT/DAD = 1

DAC tone generator mode, hardware-program DAC by setting DAT7 ~ DAT0 register

bits, enable DAC tone generator。

3. DAT7 ~ DAT0 = 0

Disable DAC tone generator。

(2) DAC output paths：

DAST/P67 is used to enable DAC output buffer B1. DATEN is used to enable DAC output buffer B2.

1. External：DAC output from its output buffer B1 to DAO/P67 pin。

DAST/P67 = 1

power on DAC, enable DAC output buffer B1, output sent to DAO/P67 pin。

2. Internal：DAC output from its output buffer B2 to CTCSS Sub-audio LPF。

DATEN = 1

power on DAC, enable DAC output buffer B2, output sent to CTCSS VTX3。

(3) Using 2.5V ref and DAC

ASW3

DATEN

VREF

DAST/P67

REFSEL

REFEN

CMPEN

VRSEL

Fig.17 Voltage reference control logic

“2.5V ref.” is the reference voltage used in DAC, Comparator or CTCSS. The voltage reference control logic

process these combination use. For this reference used in Comparator, you just only take care of CMPEN and

VRSEL bits. For this reference used in others, you need to set ASW3, VREF, DATEN and DAST/P67. The

following table shows the least two bits setting to logic “1” (CMPEN=VRSEL=1 or ASW3=DATEN=1 or

VREF=DATEN=1 or VREF=DAST/P67=1) will “select 2.5V and enable 2.5V ref”.

When REFSEL = 1, the 2.5V ref is select not VDD. (select 2.5V ref)

When REFEN = 1, the 2.5V ref is power on. (2.5V ref enable)

ASW3 VREF DATEN DAST/P67 CMPEN

VRSEL Function

x

x

x

x

1

1

select 2.5V ref, enable 2.5V ref, enable Comparator

1

x

1

x

x

x

select 2.5V ref, enable 2.5V ref, enable DAC,

0

1

1

x

x

x

enable buffer B2, buffer B2 output to CTCSS LPF

x

1

0

1

x

x

select 2.5V ref, enable 2.5V ref, enable DAC,

enable buffer B1, buffer B1 output to DAO/P67 pin

(4) Select DAO/P67 pin as normal I/O P67

Set DAST/P67 = 0 to select normal I/O P67.

(5) Using DAC general mode

1. DAT/DAD = 0

select DAC general mode。

2. Program DA7 ~ DA0。

3. Enable DAC, enable DAC output buffer, select DAC reference source。

(6) Using DAC tone generator mode

1.

DAT/DAD = 1

select DAC tone generator mode。

2.

Program DAT7 ~ DAT0 = 1 to 255. (If DAT7 ~ DAT0 = 0, DAC tone gen. is disabled.)。

3.

Enable DAC, enable DAC output buffer, select DAC reference source。

Ps. When DAC tone output is set to CTCSS Sub-audio LPF(ASW3=DATEN=1 or VREF=DATEN=1), it will be

forced to select 2.5V ref by voltage reference control logic. When its output is set to DAO/P67 pin, reference

voltage can be selected as VDD or 2.5V.

Ref to Page 18,19 for CTCSS tone generation table.