HCS08 datasheet(112/198 Pages) NXP

112 / 198 page

Analog-to-Digital Converter (S08ADC10V1)

MC9S08QD4 Series MCU Data Sheet, Rev. 6

112

Freescale Semiconductor

8.4.5

Automatic Compare Function

The compare function can be configured to check for either an upper limit or lower limit. After the input

is sampled and converted, the result is added to the two’s complement of the compare value (ADCCVH

and ADCCVL). When comparing to an upper limit (ACFGT = 1), if the result is greater-than or equal-to

the compare value, COCO is set. When comparing to a lower limit (ACFGT = 0), if the result is less than

the compare value, COCO is set. The value generated by the addition of the conversion result and the two’s

complement of the compare value is transferred to ADCRH and ADCRL.

Upon completion of a conversion while the compare function is enabled, if the compare condition is not

true, COCO is not set and no data is transferred to the result registers. An ADC interrupt is generated upon

the setting of COCO if the ADC interrupt is enabled (AIEN = 1).

NOTE

The compare function can be used to monitor the voltage on a channel while

the MCU is in either wait or stop3 mode. The ADC interrupt will wake the

MCU when the compare condition is met.

8.4.6

MCU Wait Mode Operation

The WAIT instruction puts the MCU in a lower power-consumption standby mode from which recovery

is very fast because the clock sources remain active. If a conversion is in progress when the MCU enters

wait mode, it continues until completion. Conversions can be initiated while the MCU is in wait mode by

means of the hardware trigger or if continuous conversions are enabled.

The bus clock, bus clock divided by two, and ADACK are available as conversion clock sources while in

wait mode. The use of ALTCLK as the conversion clock source in wait is dependent on the definition of

ALTCLK for this MCU. Consult the module introduction for information on ALTCLK specific to this

MCU.

A conversion complete event sets the COCO and generates an ADC interrupt to wake the MCU from wait

mode if the ADC interrupt is enabled (AIEN = 1).

8.4.7

MCU Stop3 Mode Operation

The STOP instruction is used to put the MCU in a low power-consumption standby mode during which

most or all clock sources on the MCU are disabled.

8.4.7.1

Stop3 Mode With ADACK Disabled

If the asynchronous clock, ADACK, is not selected as the conversion clock, executing a STOP instruction

aborts the current conversion and places the ADC in its idle state. The contents of ADCRH and ADCRL

are unaffected by stop3 mode.After exiting from stop3 mode, a software or hardware trigger is required to

resume conversions.

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