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Chapter 9 Analog-to-Digital Converter (ADC12B_LBA_V1)
MC9S12ZVM Family Reference Manual Rev. 1.3
Freescale Semiconductor
311
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MCU Wait Mode
Depending on the ADC Wait Mode configuration bit SWAI, the ADC either continues conversion
in MCU Wait Mode or freezes conversion at the next conversion boundary before MCU Wait Mode
is entered.
ADC behavior for configuration SWAI =1’b0:
The ADC continues conversion during Wait Mode according to the conversion flow control
sequence. It is assumed that the conversion flow control sequence is continued (conversion flow
control bits TRIG, RSTA, SEQA, and LDOK are serviced accordingly).
ADC behavior for configuration SWAI = 1’b1:
At MCU Wait Mode request the ADC should be idle (no conversion or conversion sequence or
Command Sequence List ongoing).
If a conversion, conversion sequence, or CSL is in progress when an MCU Wait Mode request is
issued, a Sequence Abort Event occurs automatically and any ongoing conversion finish. After the
Sequence Abort Event finishes, if the STR_SEQA bit is set (STR_SEQA=1), then the conversion
result is stored and the corresponding flags are set. If the STR_SEQA bit is cleared
(STR_SEQA=0), then the conversion result is not stored and the corresponding flags are not set.
Alternatively the Sequence Abort Event can be issued by software before MCU Wait Mode request.
As soon as flag SEQAD_IF is set, the MCU Wait Mode request can be issued.
With the occurrence of the MCU Wait Mode request until exit from Wait Mode all flow control
signals (RSTA, SEQA, LDOK, TRIG) are cleared.
After exiting MCU Wait Mode, the following happens in the order given with expected event(s)
depending on the conversion flow control mode:
— In ADC conversion flow control mode “Trigger Mode”, a Restart Event is expected to occur.
This simultaneously sets bit TRIG and RSTA causing the ADC to execute the Restart Event
(CMD_IDX and RVL_IDX cleared) followed by the Trigger Event. The Restart Event can be
generated automatically after exit from MCU Wait Mode if bit AUT_RSTA is set.
— In ADC conversion flow control mode “Restart Mode”, a Restart Event is expected to set bit
RSTA only (ADC already aborted at MCU Wait Mode entry hence bit SEQA must not be set
simultaneously) causing the ADC to execute the Restart Event (CDM_IDX and RVL_IDX
cleared). The Restart Event can be generated automatically after exit from MCU Wait Mode if
bit AUT_RSTA is set.
— The RVL buffer select (RVL_SEL) is not changed if a CSL is in process at MCU Wait Mode
request. Hence the same RVL buffer will be used after exit from Wait Mode that was used when
Wait Mode request occurred.