mc9s12xs128 Freescale Semiconductor, Inc, mc9s12xs128 Datasheet - Page 292

• Manufacturer Part Number: mc9s12xs128
• Description: Hcs12 Microcontrollers 16-bit Automotive Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

Analog-to-Digital Converter (ADC12B16CV1)
10.4
The ADC12B16C is structured into an analog sub-block and a digital sub-block.
10.4.1
The analog sub-block contains all analog electronics required to perform a single conversion. Separate
power supplies V
10.4.1.1
The Sample and Hold (S/H) Machine accepts analog signals from the external world and stores them as
capacitor charge on a storage node.
During the sample process the analog input connects directly to the storage node.
The input analog signals are unipolar and must fall within the potential range of V
During the hold process the analog input is disconnected from the storage node.
10.4.1.2
The analog input multiplexer connects one of the 16 external analog input channels to the sample and hold
machine.
10.4.1.3
The A/D Machine performs analog to digital conversions. The resolution is program selectable at either 8
or 10 or 12 bits. The A/D machine uses a successive approximation architecture. It functions by comparing
the stored analog sample potential with a series of digitally generated analog potentials. By following a
binary search algorithm, the A/D machine locates the approximating potential that is nearest to the
sampled potential.
When not converting the A/D machine is automatically powered down.
Only analog input signals within the potential range of V
in a non-railed digital output code.
10.4.2
This subsection explains some of the digital features in more detail. See
Descriptions”
10.4.2.1
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 external trigger signal (out of reset ATD channel 15, configurable in ATDCTL1) is programmable to
292
Functional Description
Analog Sub-Block
Digital Sub-Block
Sample and Hold Machine
Analog Input Multiplexer
Analog-to-Digital (A/D) Machine
External Trigger Input
for all details.
DDA
and V
SSA
allow to isolate noise of other MCU circuitry from the analog sub-block.
S12XS Family Reference Manual, Rev. 1.10
RL
to V
RH
(A/D reference potentials) will result
Section 10.3.2, “Register
SSA
Freescale Semiconductor
to V
DDA
.