mc9s12c32mpb16 Freescale Semiconductor, Inc, mc9s12c32mpb16 Datasheet - Page 246

• Manufacturer Part Number: mc9s12c32mpb16
• Description: Hcs12 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

Chapter 8 Analog-to-Digital Converter (ATD10B8C) Block Description
8.4.2
This subsection explains some of the digital features in more detail. See 7 for all details.
8.4.2.1
The external trigger feature allows the user to synchronize ATD conversions to the external environment
events rather than relying on software to signal the ATD module when ATD conversions are to take place.
The input signal (ATD channel 7) is programmable to be edge or level sensitive with polarity control.
Table 8-19
external trigger function
During a conversion, if additional active edges are detected the overrun error flag ETORF is set.
In either level or edge triggered modes, the first conversion begins when the trigger is received. In both
cases, the maximum latency time is one Bus Clock cycle plus any skew or delay introduced by the trigger
circuitry.
Once ETRIGE is enabled, conversions cannot be started by a write to ATDCTL5, but rather must be
triggered externally.
If the level mode is active and the external trigger both de-asserts and re-asserts itself during a conversion
sequence, this does not constitute an overrun; therefore, the flag is not set. If the trigger is left asserted in
level mode while a sequence is completing, another sequence will be triggered immediately.
246
.
ETRIGLE
X
X
0
0
1
1
gives a brief description of the different combinations of control bits and their affect on the
Digital Sub-block
External Trigger Input (ETRIG)
The conversion results for the external trigger ATD channel 7 have no
meaning while external trigger mode is enabled.
ETRIGP
X
X
0
1
0
1
ETRIGE
Table 8-19. External Trigger Control Bits
0
0
1
1
1
1
MC9S12C-Family / MC9S12GC-Family
SCAN
X
X
X
X
0
1
Rev 01.23
NOTE
Ignores external trigger. Performs one conversion sequence
and stops.
Ignores external trigger. Performs continuous conversion
sequences.
Falling edge triggered. Performs one conversion sequence
per trigger.
Rising edge triggered. Performs one conversion sequence
per trigger.
Trigger active low. Performs continuous conversions while
trigger is active.
Trigger active high. Performs continuous conversions while
trigger is active.
Description
Freescale Semiconductor