AT89C5132-ROTIL datasheet(148/182 Pages) ATMEL

148 / 182 page

148

4173E–USB–09/07

AT89C5132

Figure 21-2. Timing Diagram

21.1.1

Clock Generator

The ADC clock is generated by division of the peripheral clock (see details in Section “X2 Fea-

ture”, page 12). The division factor is then given by ADCP4:0 bits in ADCLK register. Figure 21-

3 shows the ADC clock generator and its calculation formula(1).

Figure 21-3. ADC Clock Generator and Symbol Caution:

Note:

1. In all cases, the ADC clock frequency may be higher than the maximum FADCLK parameter

reported in the Section “Analog to Digital Converter”, page 201.

2. The ADCD value of 0 is equivalent to an ADCD value of 32.

21.1.2

Channel Selection

The channel on which conversion is performed is selected by the ADCS bit in ADCON register

according to Table 30.

Table 30. ADC Channel Selection

21.1.3

Conversion Precision

The 10-bit precision conversion is achieved by stopping the CPU core activity during conversion

for limiting the digital noise induced by the core. This mode called the Pseudo-Idle mode(1),(2) is

enabled by setting the ADIDL bit in ADCON register(3). Thus, when conversion is launched (see

Section "Conversion Launching", page 149), the CPU core is stopped until the end of the con-

ADEN

ADSST

ADEOC

SETUP

CONV

CLK

ADCLK

ADCD4:0

ADCLK

ADC Clock

ADCclk

PERclk

2 ADCD

⋅

-------------------------

ADC Clock Symbol

ADC

CLOCK

PER

CLOCK

ADCS

Channel

AIN1

AIN0

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