T89C51CC02CA-RATIM datasheet(126/159 Pages) ATMEL

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126

AT/T89C51CC02

4126L–CAN–01/08

Analog-to-Digital

Converter (ADC)

This section describes the on-chip 10-bit analog-to-digital converter of the

T89C51CC02. Eight ADC channels are available for sampling of the external sources

AN0 to AN7. An analog multiplexer allows the single ADC converter to select one from

the 8 ADC channels as ADC input voltage (ADCIN). ADCIN is converted by the 10-bit-

cascaded potentiometric ADC.

Two modes of conversion are available:

- Standard conversion (8 bits).

- Precision conversion (10 bits).

For the precision conversion, set bit PSIDLE in ADCON register and start conversion.

The device is in a pseudo-idle mode, the CPU does not run but the peripherals are

always running. This mode allows digital noise to be as low as possible, to ensure high

precision conversion.

For this mode it is necessary to work with end of conversion interrupt, which is the only

way to wake the device up.

If another interrupt occurs during the precision conversion, it will be served only after

this conversion is completed.

Features

•

8 channels with multiplexed inputs

•

10-bit cascaded potentiometric ADC

•

Conversion time 16 micro-seconds (typ.)

•

Zero Error (offset) ± 2 LSB max

•

Positive External Reference Voltage Range (VAREF) 2.4 to 3.0-volt (typ.)

•

ADCIN Range 0 to 3-volt

•

Integral non-linearity typical 1 LSB, max. 2 LSB

•

Differential non-linearity typical 0.5 LSB, max. 1 LSB

•

Conversion Complete Flag or Conversion Complete Interrupt

•

Selectable ADC Clock

ADC Port1 I/O Functions

Port 1 pins are general I/O that are shared with the ADC channels. The channel select

bit in ADCF register define which ADC channel/port1 pin will be used as ADCIN. The

remaining ADC channels/port1 pins can be used as general purpose I/O or as the alter-

nate function that is available.

A conversion launched on a channel which are not selected on ADCF register will not

have any effect.

VAREF

VAREF should be connected to a low impedance point and must remain in the range

specified VAREF absolute maximum range (See section “AC-DC”).

. If the ADC is not used, it is recommended to tie VAREF to VAGND.

T89C51CC02CA-RATIM Datasheet(PDF) 126 Page - ATMEL Corporation

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