SLAU144K 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
The low-frequency mode is selected when UCOS16 = 0. This mode allows generation of baud rates from low frequency clock sources (for example, 9600 baud from a 32768-Hz crystal). By using a lower input frequency the power consumption of the module is reduced. Using this mode with higher frequencies and higher prescaler settings will cause the majority votes to be taken in an increasingly smaller window and thus decrease the benefit of the majority vote.
In low-frequency mode the baud rate generator uses one prescaler and one modulator to generate bit clock timing. This combination supports fractional divisors for baud rate generation. In this mode, the maximum USCI baud rate is one-third the UART source clock frequency BRCLK.
Timing for each bit is shown in Figure 15-10. For each bit received, a majority vote is taken to determine the bit value. These samples occur at the N/2 - 1/2, N/2, and N/2 + 1/2 BRCLK periods, where N is the number of BRCLKs per BITCLK.
Modulation is based on the UCBRSx setting as shown in Table 15-2. A 1 in the table indicates that m = 1 and the corresponding BITCLK period is one BRCLK period longer than a BITCLK period with m = 0. The modulation wraps around after 8 bits but restarts with each new start bit.
UCBRSx | Bit 0 (Start Bit) | Bit 1 | Bit 2 | Bit 3 | Bit 4 | Bit 5 | Bit 6 | Bit 7 |
---|---|---|---|---|---|---|---|---|
0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
1 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | 0 |
2 | 0 | 1 | 0 | 0 | 0 | 1 | 0 | 0 |
3 | 0 | 1 | 0 | 1 | 0 | 1 | 0 | 0 |
4 | 0 | 1 | 0 | 1 | 0 | 1 | 0 | 1 |
5 | 0 | 1 | 1 | 1 | 0 | 1 | 0 | 1 |
6 | 0 | 1 | 1 | 1 | 0 | 1 | 1 | 1 |
7 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |