4501 datasheet(64/212 Pages) RENESAS

64 / 212 page

1-52

Rev.2.01

Feb 07, 2005

4501 Group

HARDWARE

REJ09B0192-0201

Fig. 53 Analog input external circuit example-1

Fig. 54 Analog input external circuit example-2

Notes for the use of A/D conversion 1

Note the following when using the analog input pins also for port

P2 function:

• Selection of analog input pins

Even when P20/AIN0 and P21/AIN1 are set to pins for analog in-

put, they continue to function as port P2 input/output.

Accordingly, when any of them are used as I/O port and others

are used as analog input pins, make sure to set the outputs of

pins that are set for analog input to “1.” Also, the port input func-

tion of the pin functions as an analog input is undefined.

• TALA instruction

When the TALA instruction is executed, the low-order 2 bits of

multaneously, the low-order 2 bits of register A is “0.”

Notes for the use of A/D conversion 2

Do not change the operating mode (both A/D conversion mode

and comparator mode) of A/D converter with the bit 3 of register

Q1 while the A/D converter is operating.

When the operating mode of A/D converter is changed from the

comparator mode to A/D conversion mode with the bit 3 of regis-

ter Q1, note the following;

• Clear the bit 2 of register V2 to “0” (refer to Figure 52➀) to

change the operating mode of the A/D converter from the com-

parator mode to A/D conversion mode with the bit 3 of register

Q1.

• The A/D conversion completion flag (ADF) may be set when the

operating mode of the A/D converter is changed from the com-

parator mode to the A/D conversion mode. Accordingly, set a

value to the bit 3 of register Q1, and execute the SNZAD instruc-

tion to clear the ADF flag.

; (✕0✕✕2)

TV2A

; The SNZAD instruction is valid ........ ➀

; (0✕✕✕2)

TQ1A

; Operation mode of A/D converter is

changed from comparator mode to A/D

conversion mode.

SNZAD

NOP

✕ : these bits are not used here.

Fig. 52 A/D conversion interrupt program example

Notes for the use of A/D conversion 3

Each analog input pin is equipped with a capacitor which is used

to compare the analog voltage. Accordingly, when the analog

voltage is input from the circuit with high-impedance and, charge/

discharge noise is generated and the sufficient A/D accuracy

may not be obtained. Therefore, reduce the impedance or, con-

nect a capacitor (0.01

µF to 1 µF) to analog input pins (Figure 53).

When the overvoltage applied to the A/D conversion circuit may

occur, connect an external circuit in order to keep the voltage

within the rated range as shown the Figure 54. In addition, test

the application products sufficiently.

Sensor

AIN

Apply the voltage withiin the specifications

to an analog input pin.

Sensor

AIN

About 1k

Ω

LIST OF PRECAUTIONS

Electric Characteristic Differences Between Mask ROM and One

Time PROM Version MCU

There are differences in electric characteristics, operation margin,

noise immunity, and noise radiation between Mask ROM and One

Time PROM version MCUs due to the difference in the manufac-

turing processes.

When manufacturing an application system with the One time

PROM version and then switching to use of the Mask ROM ver-

sion, please perform sufficient evaluations for the commercial

samples of the Mask ROM version.

Note on Power Source Voltage

When the power source voltage value of a microcomputer is less

than the value which is indicated as the recommended operating

conditions, the microcomputer does not operate normally and

may perform unstable operation.

In a system where the power source voltage drops slowly when

the power source voltage drops or the power supply is turned off,

reset a microcomputer when the supply voltage is less than the

recommended operating conditions and design a system not to

cause errors to the system by this unstable operation.

External clock

When the external signal clock is used as the source oscillation

(f(XIN)), note that the RAM back-up mode (POF and POF2 in-

structions) cannot be used.

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