note for 430（注意 430）.docVIP

note for 430（注意 430） MSP430G2553MSP430F5529_Learn_Note A, IO / P2.6, P2.7 as a common IO port, in need of a set of P2SEL=~ (BIT6+BIT7); /////////////// port /////////////////////// / MSP microcontroller power when the default input state, so initialized to change direction. This will prevent IO interference. Do not use the IO port to deal with, it is best not vacant, through the current limiting resistor grounding or VDD direct grounding line. 0 input mode, read only. 1 output mode, read and write. X The role of PxREN is to enable pull-up or pull-down resistors, because the internal MSP430F5438 microcontroller IO port integrated pullup or pulldown resistor, Through the PxREN to enable the two resistance. In addition, there are two kinds of input and output state of the IO port, IO port is when the output state, IO port level is controlled by MCU; when the IO port input state, IO level is determined by the external circuit. IO port input and output state choice decided by PxDIR, when PxDIR=0 corresponding to the input state of the IO port, the output state corresponding to the PxDIR=1 IO port. The role of PxOUT when IO is configured as the output state, determines the output level, when the IO is configured as input state And, when can pull down resistor, whether it is pulled up or down resistance effect. PxREN control register pull resistance is enabled, PxOUT decided to pull up or pull down resistor, the specific working principle is this PxDIR=1 output PxREN=1 only works PxOUT=1 pull and pull resistance PxOUT=0 drop No PxREN=0 push-pull output PxOUT=1 output high resistance The PxOUT=0 output is low PxDIR=0 PxREN=1 input PxOUT=1 pull-up resistance effect PxOUT=0 drop PxREN=0 IO in a high impedance state to a high impedance state Two, clock X Mainly to provide three clock output: auxiliary clock ACLK (Auxillary Clock), MCLK (Main System Clock system clock) and SMCLK (Sub System system clock Clock). ///G2553 1, ACLK: system clock, from LFXT1CLK to 32768HZ. 2, MCLK: