Analog-to-Digital Converter (ADC12)
MCF51CN128 Reference Manual, Rev. 6
15-8
Freescale Semiconductor
15.3.2
Status and Control Register 2 (ADCSC2)
The ADCSC2 register controls the compare function, conversion trigger, and conversion active of the
ADC module.
15.3.3
Data Result High Register (ADCRH)
In 12-bit operation, ADCRH contains the upper four bits of the result of a 12-bit conversion. In 10-bit
mode, ADCRH contains the upper two bits of the result of a 10-bit conversion. When configured for 10-bit
mode, ADR[11:10] are cleared. When configured for 8-bit mode, ADR11 – ADR8 are equal to zero.
In 12-bit and 10-bit mode, ADCRH is updated each time a conversion completes except when automatic
compare is enabled and the compare condition is not met. In 12-bit and 10-bit mode, reading ADCRH
prevents the ADC from transferring subsequent conversion results into the result registers until ADCRL
is read. If ADCRL is not read until after the next conversion is completed, the intermediate conversion
result is lost. In 8-bit mode, there is no interlocking with ADCRL.
7
6
5
4
3
2
1
0
R
ADACT
ADTRG
ACFE
ACFGT
0
0
R
1
1
Bits 1 and 0 are reserved bits that must always be written to 0.
R
1
W
Reset:
0
0
0
0
0
0
0
0
Figure 15-3. Status and Control Register 2 (ADCSC2)
Table 15-5. ADCSC2 Register Field Descriptions
Field
Description
7
ADACT
Conversion Active. Indicates that a conversion is in progress. ADACT is set when a conversion is initiated and
cleared when a conversion is completed or aborted.
0 Conversion not in progress
1 Conversion in progress
6
ADTRG
Conversion Trigger Select. Selects the type of trigger used for initiating a conversion. Two types of trigger are
selectable: software trigger and hardware trigger. When software trigger is selected, a conversion is initiated
following a write to ADCSC1. When hardware trigger is selected, a conversion is initiated following the assertion
of the ADHWT input.
0 Software trigger selected
1 Hardware trigger selected
5
ACFE
Compare Function Enable. Enables the compare function.
0 Compare function disabled
1 Compare function enabled
4
ACFGT
Compare Function Greater Than Enable. Configures the compare function to trigger when the result of the
conversion of the input being monitored is greater than or equal to the compare value. The compare function
defaults to triggering when the result of the compare of the input being monitored is less than the compare value.
0 Compare triggers when input is less than compare level
1 Compare triggers when input is greater than or equal to compare level
