MPC5604B/C Microcontroller Reference Manual, Rev. 8
594 Freescale Semiconductor
The MSR[NSTART] status bit is automatically set when the normal conversion starts. At the same time
the MCR[NSTART] bit 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 interrupt controller chapter for
further details) is immediately issued after the start of conversion.
25.3.1.3 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 MCR[MODE] bit. 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 25-2.
Figure 25-2. 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.
Table 25-1. Configurations for starting normal conversion
Type of
conversion
start
MCR MSR
Result
TRGEN
NSTAR
T
EDGLE
V
EDGE
NSTAR
T
Software 0 1 — — 1 Conversion chain starts
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.
Trigger11101The 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.
Sample B Convert B Sample C Sample D Convert D Sample E Convert EConvert C
To Next Page
