PXD20RM Datasheet, PDF (168/1628 Pages) Freescale Semiconductor, Inc – PXD20 Microcontroller

Table 5-21. Configurations for starting normal conversion (continued)
Type of
conversion
start TRGEN
MCR
NSTAR EDGLE
T
V
EDGE
MSR
NSTAR
T
Result
Trigger
1
—
0
0
1 A falling edge detected in a trigger signal sets the
NSTART bit in the MSR and starts the
programmed conversion.
1
A rising edge detected in a trigger signal sets the
NSTART bit in the MSR and starts the
programmed conversion.
Trigger
1
1
1
0
1 The conversion is started if the programmed level
on the trigger signal is detected: the start of
conversion is enabled if the external pin is low.
1
1 The conversion is started if the programmed level
on the trigger signal is detected: the start of
conversion is enabled if the external pin is high.
The NSTART status bit in the MSR is automatically set when the normal conversion starts. At the same
time the NSTART bit in the MCR is reset, allowing the software to program a new start of conversion. In
that case the new requested conversion starts after the running conversion is completed.
If the content of all the normal conversion mask registers is zero (that is, no channel is selected) the
conversion operation is considered completed and the interrupt ECH (see further) is immediately issued
after the start of conversion.
5.4.1.3 Normal conversion operating modes
Two operating modes are available for the normal conversion:
• One Shot
• Scan
To enter one of these modes, it is necessary to program the MODE bit in the MCR. The first phase of the
conversion process involves sampling the analog channel and the next phase involves the conversion phase
when the sampled analog value is converted to digital as shown in Figure 5-25.
Sample B Convert B Sample C Convert C Sample D Convert D Sample E Convert E
Figure 5-25. Normal conversion flow
In One Shot Mode (MODE = 0) a sequential conversion specified in the NCMR registers is performed
only once. At the end of each conversion, the digital result of the conversion is stored in the corresponding
data register.
5-26
PXD20 Microcontroller Reference Manual, Rev. 1
Preliminary—Subject to Change Without Notice
Freescale Semiconductor