7477 datasheet(156/354 Pages) RENESAS

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1-139

7470/7471/7477/7478 GROUP USER’S MANUAL

HARDWARE

1.14 A-D converter

Fig. 1.14.1 A-D converter block diagram

1.14 A-D converter

In the 7470/7471/7477/7478 group, the following A-D converter is incorporated.

q Analog input pins…… 7470/7477 group: 4 channels (in common with Port P2)

7471/7478 group: 8 channels (in common with Port P2)

q Conversion method… Successive approximation comparison

In the 7470/7471 group, when the A-D converter is not used, power dissipation can be suppressed by the

VREF switch. (The 7477/7478 group is not provided with this function.)

Figure 1.14.1 shows a block diagram of the A-D converter.

P20/IN0

P21/IN1

P22/IN2

P23/IN3

P24/IN4

P25/IN5

P26/IN6

P27/IN7

VSS

VREF

Data bus

(Note 2)

A-D control register

(Address 00D916)

Comparator

A-D control circuit

A-D conversion register

(Address 00DA16)

(Note 1)

Switch tree

Resistor ladder

A-D conversion

interrupt request

VREF switch (Note 2)

Notes 1. The 7470/7477 group is not provided with the P2 /IN4–P27/IN7 pins.

2. The 7477/7478 group is not provided with the V

switch and the V

connection selection bit

(bit 4) of the A-D control register.

REF

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