STM8S datasheet(433/467 Pages) STMICROELECTRONICS

433 / 467 page

DocID14587 Rev 14

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RM0016

Analog/digital converter (ADC)

454

Note:

When using scan mode, it is not possible to use channels AIN0 to AINn in output mode

because the output stage of each channel is disabled when it is selected by the ADC

multiplexer.

A single conversion is performed for each channel starting with AIN0 and the data is stored

in the data buffer registers ADC_DBxR. When the last channel (channel ‘n’) has been

converted, the EOC (End of Conversion) flag is set and an interrupt is generated if the

EOCIE bit is set.

The converted values for each channel can be read from the data buffer registers. The OVR

flag is set if one of the data buffer registers is overwritten before it has been read (see

Section 24.5.5).

Do not clear the SCAN bit while the conversion sequence is in progress. Single scan mode

can be stopped immediately by clearing the ADON bit.

To start a new SCAN conversion, clear the EOC bit and set the ADON bit in the ADC_CR1

Continuous scan mode

This mode is like single scan mode except that each time the last channel has been

converted, a new scan conversion from channel 0 to channel n starts automatically. The

OVR flag is set if one of the data buffer registers is overwritten before it has been read (see

Section 24.5.5).

Continuous scan mode is started by setting the ADON bit while the SCAN and CONT bits

are set.

Do not clear the SCAN bit while scan conversion is in progress.

Continuous scan mode can be stopped immediately by clearing the ADON bit. Alternatively

if the CONT bit is cleared while conversion is ongoing, conversion stops the next time the

last channel has been converted.

Caution:

In scan mode, do not use a bit manipulation instruction (BRES) to clear the EOC flag. This is

because this performs a read-modify-write on the whole ADC_CSR register, reading the

current channel number from the CH[3:0] register and writing it back, which changes the last

channel number for the scan sequence.

The correct way to clear the EOC flag in continuous scan mode is to load a byte in the

ADC_CSR register from a RAM variable, clearing the EOC flag and reloading the last

channel number for the scan sequence

24.5.5

Overrun flag

The OVR error flag is set by hardware in buffered continuous mode, single scan or

continuous scan modes. It indicates that one of the ten data buffer registers was overwritten

by a new converted value before the previous value was read. In this case, it is

recommended to start a new conversion.

Note:

Setting the ADON bit automatically clears the OVR flag.

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