
Analog-to-Digital Converter (ADC)
PXN20 Microcontroller Reference Manual, Rev. 1
34-42
Freescale Semiconductor
If the START bit in MCR is reset while ADC is converting, the user needs to wait for the ADC to finish
the current chain conversion (i.e., ECH interrupt) before setting the START bit once again.
34.4.1.3
Normal Conversion Operating Modes
Two operating modes are available for the normal conversion:
•
One Shot mode
•
Scan mode
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 34-39. Normal Conversion Flow
In
One Shot mode
(MODE = 0), a sequential conversion specified in the NCMR
n
mask register is
performed only once. At the end of each conversion, the digital result of the conversion is stored into the
corresponding data register.
For example: Channels A-B-C-D-E-F-G-H are present in the device where channels B-D-E are to be
converted in the One Shot mode. MODE = 0 is set for One Shot mode. Conversion starts from the channel
B followed by conversion of channels D-E. At the end of conversion of channel E the scanning of channels
stops.
The MSR[NSTART] status bit is automatically set when the normal conversion starts. At the same time
MCR[NSTART] 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.
In
Scan mode
(MODE = 1), a sequential conversion of channels specified in the NCMR
n
register is
continuously performed. As in the previous case, at the end of each conversion the digital result of the
conversion is stored into the corresponding data register.
The MSR[NSTART] bit is automatically set when the normal conversion starts. Unlike One Shot mode,
the MCR[NSTART] is not reset. It can be reset by software when the user needs to stop scan mode. In that
case, the ADC completes the current scan conversion and after the last conversion resets MSR[NSTART]
as well.
For Example: Channels A-B-C-D-E-F-G-H are present in the device where channels B-D-E are to be
converted in the Scan mode. MODE = 1 is set for Scan mode. Conversion starts from the channel B
followed by conversion of the channels D – E. At the end of conversion of channel E the scanning of
channel B starts followed by conversion of the channels D – E. This sequence repeats itself until the
NSTART bit of MCR is reset by software.
If the conversion is started by an external trigger and EDGLEV = 0, MCR[NSTART] bit is not set. As a
consequence, once started the only way to stop scan mode conversion is to set MODE = 0.
Sample B
Convert B
Sample C
Convert C
Sample D
Convert D
Sample E
Convert E
Содержание PXN2020
Страница 1: ...PXN20 Microcontroller Reference Manual Devices Supported PXN2020 PXN2120 PXN20RM Rev 1 06 2011...
Страница 42: ...PXN20 Microcontroller Reference Manual Rev 1 lxiv Freescale Semiconductor...
Страница 64: ...Introduction PXN20 Microcontroller Reference Manual Rev 1 1 22 Freescale Semiconductor...
Страница 112: ...Signal Description PXN20 Microcontroller Reference Manual Rev 1 3 44 Freescale Semiconductor...
Страница 118: ...Resets PXN20 Microcontroller Reference Manual Rev 1 4 6 Freescale Semiconductor...
Страница 162: ...Clocks Reset and Power CRP PXN20 Microcontroller Reference Manual Rev 1 6 30 Freescale Semiconductor...
Страница 182: ...Frequency Modulated Phase Locked Loop FMPLL PXN20 Microcontroller Reference Manual Rev 1 7 20 Freescale Semiconductor...
Страница 268: ...Boot Assist Module BAM PXN20 Microcontroller Reference Manual Rev 1 9 14 Freescale Semiconductor...
Страница 318: ...Interrupts and Interrupt Controller INTC PXN20 Microcontroller Reference Manual Rev 1 10 50 Freescale Semiconductor...
Страница 326: ...General Purpose Static RAM SRAM PXN20 Microcontroller Reference Manual Rev 1 11 8 Freescale Semiconductor...
Страница 372: ...e200z6 Core Z6 PXN20 Microcontroller Reference Manual Rev 1 13 8 Freescale Semiconductor...
Страница 412: ...e200z0 Core Z0 PXN20 Microcontroller Reference Manual Rev 1 14 14 Freescale Semiconductor...
Страница 460: ...Memory Protection Unit MPU PXN20 Microcontroller Reference Manual Rev 1 18 20 Freescale Semiconductor...
Страница 478: ...Error Correction Status Module ECSM PXN20 Microcontroller Reference Manual Rev 1 19 18 Freescale Semiconductor...
Страница 488: ...Software Watchdog Timer SWT PXN20 Microcontroller Reference Manual Rev 1 20 10 Freescale Semiconductor...
Страница 494: ...System Timer Module STM PXN20 Microcontroller Reference Manual Rev 1 21 6 Freescale Semiconductor...
Страница 821: ...Media Local Bus MLB PXN20 Microcontroller Reference Manual Rev 1 Freescale Semiconductor 27 49...
Страница 822: ...Media Local Bus MLB PXN20 Microcontroller Reference Manual Rev 1 27 50 Freescale Semiconductor...
Страница 926: ...Controller Area Network FlexCAN PXN20 Microcontroller Reference Manual Rev 1 29 42 Freescale Semiconductor...
Страница 990: ...Deserial Serial Peripheral Interface DSPI PXN20 Microcontroller Reference Manual Rev 1 30 64 Freescale Semiconductor...
Страница 1044: ...Enhanced Serial Communication Interface eSCI PXN20 Microcontroller Reference Manual Rev 1 31 54 Freescale Semiconductor...
Страница 1080: ...Cross Triggering Unit CTU PXN20 Microcontroller Reference Manual Rev 1 33 12 Freescale Semiconductor...
Страница 1134: ...Analog to Digital Converter ADC PXN20 Microcontroller Reference Manual Rev 1 34 54 Freescale Semiconductor...
Страница 1150: ...IEEE 1149 1 Test Access Port Controller JTAGC PXN20 Microcontroller Reference Manual Rev 1 35 16 Freescale Semiconductor...
Страница 1257: ...Nexus Development Interface NDI PXN20 Microcontroller Reference Manual Rev 1 Freescale Semiconductor 36 107...
Страница 1258: ...Nexus Development Interface NDI PXN20 Microcontroller Reference Manual Rev 1 36 108 Freescale Semiconductor...
Страница 1376: ...Memory Map PXN20 Microcontroller Reference Manual Rev 1 A 118 Freescale Semiconductor...