STM8S datasheet(432/467 Pages) STMICROELECTRONICS

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Analog/digital converter (ADC)

RM0016

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DocID14587 Rev 14

24.5.3

Channel selection

There are up to 16 external input channels that can be selected through CH[0:3] bits of the

ADC_CSR register. The number of external channels depends on the device (refer to the

product datasheets).

If the channel selection is changed during a conversion, the current conversion is reset and

a new start pulse is sent to the ADC.

24.5.4

Conversion modes

The ADC supports five conversion modes: single mode, continuous mode, buffered

continuous mode, single scan mode, continuous scan mode.

Note:

ADC1 AIN12 channel cannot be selected in ADC scan mode or with analog watchdog.

Values converted from AIN12 are stored only in the ADC_DRH/ADC_DRL registers. Refer

to product datasheet for AIN12 availability.

Single mode

In Single conversion mode, the ADC does one conversion on the channel selected by the

CH[3:0] bits in the ADC_CSR register. This mode is started by setting the ADON bit in the

ADC_CR1 register, while the CONT bit is 0.

Once the conversion is complete, the converted data are stored in the ADC_DR register, the

EOC (End of Conversion) flag is set and an interrupt is generated if the EOCIE bit is set.

Continuous and buffered continuous modes

In continuous conversion mode, the ADC starts another conversion as soon as it finishes

one. This mode is started by setting the ADON bit in the ADC_CR1 register, while the CONT

bit is set.

•

If buffering is not enabled (DBUF bit = 0 in the ADC_CR3 register), the converted data

is stored in the ADC_DR register and the EOC (End of Conversion) flag is set. An

interrupt is generated if the EOCIE bit is set. Then a new conversion starts

automatically.

•

If buffering is enabled (DBUF bit =1) the data buffer is filled with the results of 8 or 10

consecutive conversions performed on a single channel. When the buffer is full, the

EOC (End of Conversion) flag is set and an interrupt is generated if the EOCIE bit is

set. Then a new set of 8 or 10 conversions 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).

To stop continuous conversion, reset the CONT bit to stop conversion or reset the ADON bit

to power off the ADC.

Single scan mode

This mode is used to convert a sequence of analog channels from AIN0 to AINn where ‘n’ is

the channel number defined by the CH[3:0] bits in the ADC_CSR register. During the scan

conversion sequence the CH[3:0] bits are updated by hardware and contain the channel

number currently being converted.

Single scan mode is started by setting the ADON bit while the SCAN bit is set and the

CONT bit is cleared.

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