M32CSLASH8B datasheet(395/406 Pages) RENESAS

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M32C/8B Group

25. Usage Notes

Preliminary specification

Specifications in this manual are tentative and subject to change.

REJ09B0450-0050 Rev.0.50 Oct 31, 2008

Page 378 of 385

25.12 A/D Converter

• Set the ADST bit to 1 (A/D conversion starts) after setting registers AD0CON0 (ADST bit excluded),

AD0CON1, AD0CON2, AD0CON3, and AD0CON4.

• When the VCUT bit in the AD0CON1 register is changed from 0 (VREF not connected) to 1 (VREF

connected), wait for 1

μs or more to start A/D conversion.

Set the VCUT bit to 0 when A/D conversion is not used to reduce current consumption.

•To prevent latch-up and malfunction due to noise and also to minimize a conversion error, insert a capacitor

between the AVSS pin and each of the following pins: the AVCC pin, VREF pin, or analog input pin ANi_j

(i = none, 0, 2, 15; j = 0 to 7). Insert a capacitor between the VCC pin and the VSS pin as well. Figure 25.4

shows an example of individual pin handling.

Figure 25.4

Individual Pin Handling

• Set the port direction bit in the PDk register (k = 0 to 15), which corresponds to a pin used as an analog input

pin, to 0 (input mode). Also, set the port direction bit in the PDk register corresponding to the ADTRG pin, to

0 (input mode.)

• When the key input interrupt is used, do not select pins P10_4 to P10_7 (AN_4 to AN_7) as analog input pins.

• φAD frequency must be 16 MHz or lower when VCC1 = 4.2 V to 5.5 V, or 10 MHz or lower when

VCC1 = 3.0 V to 5.5 V. When the sample and hold is not activated,

φAD frequency must be 250 kHz or higher.

When the sample and hold is activated,

φAD frequency must be 1 MHz or higher.

• When A/D operating mode is changed, set bits CH2 to CH0 in the AD0CON0 register or bits SCAN1 and

SCAN0 in the AD0CON1 register again to select analog input pins.

• The voltage applied to AN_0 to AN_7, AN15_0 to AN15_7, ANEX0, and ANEX1 must be VCC1 or below.

The voltage applied to AN0_0 to AN0_7, and AN2_0 to AN2_7 must be VCC2 or below.

VCC1

VSS

AVCC

AVSS

VREF

ANi

MCU

NOTES:

1. C1

≥ 0.47 μF, C2 ≥ 0.47 μF, C3 ≥ 10000 pF, C4 ≥ 0.1 μF, C5 ≥ 0.1 μF (reference values)

2. Use thick and shortest possible wiring to connect capacitors.

VCC2

VSS

VCC1

VCC2

VCC1

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