ZHCU032K December 2004 – August 2022 MSP430AFE221 , MSP430AFE222 , MSP430AFE223 , MSP430AFE231 , MSP430AFE232 , MSP430AFE233 , MSP430AFE251 , MSP430AFE252 , MSP430AFE253 , MSP430F2001 , MSP430F2002 , MSP430F2003 , MSP430F2011 , MSP430F2012 , MSP430F2013 , MSP430F2101 , MSP430F2111 , MSP430F2112 , MSP430F2121 , MSP430F2122 , MSP430F2131 , MSP430F2132 , MSP430F2132-EP , MSP430F2232 , MSP430F2234 , MSP430F2252 , MSP430F2252-Q1 , MSP430F2254 , MSP430F2272 , MSP430F2272-Q1 , MSP430F2274 , MSP430F2274-EP , MSP430F233 , MSP430F2330 , MSP430F235 , MSP430F2350 , MSP430F2370 , MSP430F2410 , MSP430F2416 , MSP430F2417 , MSP430F2418 , MSP430F2419 , MSP430F247 , MSP430F2471 , MSP430F248 , MSP430F2481 , MSP430F249 , MSP430F2491 , MSP430F2616 , MSP430F2617 , MSP430F2618 , MSP430F2619 , MSP430G2001 , MSP430G2101 , MSP430G2102 , MSP430G2111 , MSP430G2112 , MSP430G2121 , MSP430G2131 , MSP430G2132 , MSP430G2152 , MSP430G2153 , MSP430G2201 , MSP430G2201-Q1 , MSP430G2202 , MSP430G2203 , MSP430G2210 , MSP430G2211 , MSP430G2212 , MSP430G2213 , MSP430G2221 , MSP430G2230 , MSP430G2231 , MSP430G2231-Q1 , MSP430G2232 , MSP430G2233 , MSP430G2252 , MSP430G2253 , MSP430G2302 , MSP430G2303 , MSP430G2312 , MSP430G2313 , MSP430G2332 , MSP430G2333 , MSP430G2352 , MSP430G2353 , MSP430G2402 , MSP430G2403 , MSP430G2412 , MSP430G2413 , MSP430G2432 , MSP430G2433 , MSP430G2444 , MSP430G2452 , MSP430G2453 , MSP430G2513 , MSP430G2533 , MSP430G2544 , MSP430G2553 , MSP430G2744 , MSP430G2755 , MSP430G2855 , MSP430G2955 , MSP430TCH5E
为了在低功耗模式下使用,USCI 模块为 SMCLK 提供了自动时钟激活。当 SMCLK 是 USCI 的时钟源并无效时,由于器件处于一个低功耗模式,如果需要,USCI 模块都可忽略时钟源控制位设置而自动激活。直到 USCI 模块回到其空闲状态,时钟都会保持激活条件。USCI 模块恢复空闲条件后,时钟源的控制权会恢复到其控制位的设置。不为时钟信号 (ACLK) 提供自动时钟激活。
当 USCI 模块激活一个无效的时钟源时,该时钟源将为整个设备变得活跃,并且这可能会影响到任何为了使用而被配置的外围设备时钟源。例如,当 USCI 模块迫使 SMCLK 激活时,一个使用 SMCLK 的定时器将递增。
在 I2C 模式下,由于时钟是由外部主器件提供,所以就不需要内部时钟源。在器件处于 LPM4 状态下并且所有内部时钟源被禁止时,就可以实现在 I2C 受控模式中操作 USCI。接收或者发送中断可以将 CPU 从任何一种低功耗模式中唤醒。