3819 datasheet(46/218 Pages) RENESAS

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3819 Group

SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

MITSUBISHI MICROCOMPUTERS

Fig. 24 A-D converter block diagram

D-A CONVERTER

The 3819 group has internal D-A converter with 8-bit resolutions !

1 channel.

D-A conversion is performed by setting the value in the D-A con-

version register. The result of D-A conversion is output from the

DA pin by setting the DA output enable bit to “1” . At this time, the

corresponding bit (PB2/DA) of the port PB direction register should

be set to “0” (input status).

The output analog voltage V is determined with the value n

(n: decimal number) in the D-A conversion register as follows:

V=VREF ! n/256 (n=0 to 255)

VVREF: the reference voltage

At reset, the D-A conversion register is cleared to “0016”, the DA

output enable bits are cleared to “0”, and the PB2/DA pin goes to

high impedance state. The D-A output does not build in a buffer, so

connect an external buffer when driving a low-impedance load.

Set VCC to 3.0 V or more when using the D-A converter.

Fig. 25 D-A converter block diagram

Fig. 26 Equivalent connection circuit of D-A converter

A-D control circuit

A-D conversion register

Resistor ladder

VREF

AVSS

Comparator

A-D conversion interrupt request

P70/AN0

(Address 002D16)

AD-DA control register

(address 002C16)

P71/AN1

P72/AN2

P73/AN3

P74/AN4

P75/AN5

P76/AN6

P77/AN7

P50/SIN2/AN8

P51/Sout2/AN9

P52/SCLK2 /AN10

P53/SRDY2/AN11

P54/SIN3/AN12

P55/SOUT3/AN13

P56/SCLK3 /AN14

P57/SRDY3/AN15

Data bus

PB2/DA

D-A conversion register (8)

R-2R resistor ladder

DA output enable bit

AVSS

VREF

"0"

"1"

MSB

"0"

"1"

LSB

PB2/DA

D-A conversion

DA output enable bit

RRRR

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