7540 datasheet(209/366 Pages) RENESAS

209 / 366 page

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REJ09B0018-0200Z

Rev.2.00

Jun 21, 2004

7540 Group

APPLICATION

2.8 A/D converter

Fig. 2.8.8 Connection diagram

(2) Control procedure

Outline : The analog input voltage input from a sensor is converted to digital values.

Specifications : •The analog input voltage input from a sensor is converted to digital values.

•P20/AN0 pin is used as an analog input pin.

Figure 2.8.8 shows a connection diagram, and Figure 2.8.9 shows an example of control procedure.

Fig. 2.8.9 Control procedure

P20/AN0

7540 Group

Sensor

A/D conversion processing

ADCON(Address 3416)

Analog input pins: P20/AN0

Set analog input pins

0 00

ADCON(Address 3416)

Start A/D conversion

0 00

A/D conversion completed ? (Note 2)

Read ADH (address 3616) (Note 3)

RTS

Notes 1: In this case, the A/D conversion interrupt is used.

2: The completion of the A/D conversion is checked by the following;

• The A/D conversion completion bit of the A/D control register is “1”.

• The A/D conversion interrupt request bit of the interrupt request register 2 is “1”.

• Branch to the A/D conversion interrupt processing routine is executed. (In this time,

the A/D conversion interrupt is enabled.)

3: At 10-bit read: the conversion result of the high-order 2 bits (b9, b8) can be read.

At 8-bit read: Not used.

4: At 10-bit read: the conversion result of the low-order 8 bits (b7 to b0) can be read.

At 8-bit read: the conversion result of b7 to b0 can be read.

Set “0” to the A/D conversion interrupt request bit.

Set “1” to the A/D conversion interrupt enable bit.

(A/D conversion interrupt enabled) (Note 1)

Start A/D conversion

Set “0” to the A/D conversion interrupt enable bit.

(A/D conversion interrupt disabled)

Read ADL (address 3516) (Note 4)

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