概述
MSP430F149的ADC12为SAR型12位AD,共有16路输入通道，其中8路独立的外部输入通道，2路接外部Vref+,Vref-，3路内部通道可分别测内部温度传感器、AVCC、和外部参考源。 P6口第二功能为AD输入端。MSP430F149的10、11分别接外部电压参考源正负极，7脚可将内部电压参考源输出。
ADC12共有18个中断源，公用一个中断向量ADC12_VECTOR。
AD的参考源可选择内部电压参考源或外部电压参考源。内部电压参考源有1.5V,2.5V可选，使用时向ADC12CTL0写入REFON+ REF2_5V就打开了2.5V。外部电压参考源由REF+接入。上电时若不设置参考源，则参考源为系统供电电压3.3V。 2 使用方法概述 2.1程序架构 中断方式
1、设置 ADC12工作模式，启动转换，开全局中断，等待中断 2、写中断处理函数 查询方式
设置ADC12工作模式，启动转换，查询中断标志ADC12IFG
while (!(0x01 & ADC12IFG));转换完毕读取采样值，系统自动清除中断标志 2.2 使用概述 主要参数配置
设置工作方式：sing\\\\sequence\\\\re-sing\\\\re-sequencd; 设置转换时间：SHTX
设置触发方式：ADC12SC\\\\MSC\\\\TimerA\\\\ TimerB 设置通道：外部通道\\\\内部Temperature sensor 设置参考源：系统电压\\\\内部参考源\\\\外部参考源 其他细节配置
一般要配置采样转换模式为脉冲（SHP）,打开ADC12(ADC12ON),使能ADC12转换(ENC)，使能中断（如果采取中断模式），触发转换（若采用ADC12SC触发）。 解释
ADC12模数转换是在SHI的上升沿初始化的。SHI信号有四个来源： The ADC12SC bit；The Timer_A Output Unit 1； The Timer_B Output Unit 0； The Timer_B Output Unit 1。故单次采样时只需要每次设置ADC12CTL0 |= ADC12SC就采样一次；重复采样时，如Rep-sing，
设置ADC12CTL1 = SHS_1 +CONSEQ_2就选择了Rep-sing模式，每次采样通过定时器A触发。
3 相关寄存器 1、ADC12CTL0 SHT1x Bits
Sample-and-hold time(采样保持). These bits define the number of ADC12CLK cycles in the sampling period for registers ADC12MEM8 to ADC12MEM15. SHT0x Bits
Sample-and-hold time. These bits define the number of ADC12CLK cycles in the sampling period for registers ADC12MEM0 to ADC12MEM7. ADC12ON 0 ADC12 off 1 ADC12 on ENC
ENC Bit 1 Enable conversion 0 ADC12 disabled 1 ADC12 enabled
ADC12SC Bit 0 Start conversion. Software-controlled sample-and-conversion start. ADC12SC and ENC may be set together with one instruction. ADC12SC is reset automatically.
0 No sample-and-conversion-start 1 Start sample-and-conversion
MSC（多次采样/转换） Bit 7 Multiple sample and conversion. Valid only for sequence or repeated modes.
0 The sampling timer requires a rising edge of the SHI signal to trigger（触发） each sample-and-conversion.
1 The first rising edge of the SHI signal triggers the sampling timer, but further sample-and-conversions are performed automatically as soon as the prior conversion is completed. 2、ADC12CTL1 SHP
SHP Bit 9 Sample-and-hold pulse-mode select（取样保持脉冲选择模式）. This bit selects the source of the
sampling signal (SAMPCON) to be either the output of the sampling timer or the sample-input signal directly.
0 SAMPCON signal is sourced from the sample-input signal. 1 SAMPCON signal is sourced from the sampling timer. SHSx Bits 11-10
Sample-and-hold source select 00 ADC12SC bit 01 Timer_A.OUT1 10 Timer_B.OUT0 11 Timer_B.OUT1 CONSEQx Bits 2-1
Conversion sequence mode select 00 Single-channel, single-conversion 01 Sequence-of-channels 10 Repeat-single-channel 11 Repeat-sequence-of-channels 3、ADC12IE ADC12IEx Bits 15-0
Interrupt enable. These bits enable or disable the interrupt request for the ADC12IFGx bits.
0 Interrupt disabled 1 Interrupt enabled 4、ADC12IFG ADC12IFGx Bits 15-0
ADC12MEMx Interrupt flag. These bits are set when corresponding