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
接收时序有两个错误来源。第一个是比特到比特的时序误差。第二个是开始边沿出现与 USART 接受开始边沿之间的误差。图 18-9显示了 URXDx 引脚上数据和内部波特率时钟之间的异步时序误差。
理想的起始位时序 t理想 (0)是波特率时序 t波特率的一半,因为该位是在它周期的中间开始被检测的。对于剩余的字符位,理想的波特率时序 t理想(i)等于波特率时序 t波特率单个位误差可以通过以下来计算:
其中,
波特率 = 所需的波特率
BRCLK = 输入频率;为 UCLK、ACLK 或 SMCLK 选择
j = 对于开始位为 0,对于数据位 D0 为 1,依此类推
UxBR = 寄存器 UxBR1 和 UxBR0 中的分频因子
例如,满足下列条件的接收误差的计算方法:
波特率 = 2400
BRCLK = 32 768Hz (ACLK)
UxBR=13,因为理想的分频系数是 13.65
UxMCTL = 6B:m7 = 0,m6 = 1,m5 = 1,m4 = 0,m3 = 1,m2 = 0,m1 = 1,m0 = 1。UxMCTL 的 LSB 被首先使用。
结果显示每比特的误差最大为 BITCLK 周期的 5.08%。