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Software Timer_A UART in TI examples does not actually use the 32k crystal

fj604
Prodigy 40 points

MSP430G2xx1 examples include a Software UART based on Timer_A:

http://www.ti.com/cn/litv/zip/slac463a

msp430g2xx1_ta_uart9600.c         Timer_A, Ultra-Low Pwr Full-duplex UART 9600, 32kHz ACLK

Comments in the source code show that it needs a 32k crystal for ACLK:

//  ACLK = TACLK = LFXT1 = 32768Hz, MCLK = SMCLK = default DCO
//  //* An external watch crystal is required on XIN XOUT for ACLK *//   

However, ACLK is never used later in the code. I have checked and it works perfectly without a crystal. Is this a documentation error?

I thought someone might find this useful. The other example for a 2400 Baud UART does use ACLK.

  • 0
    Guru 227245 points

    You're right. These comments ar eprobably leftovers from the 1x series or other 2x devices where there is no calibration data for 1MHz DCO operation available.

    The code itself uses SMCLK for the timer, which is set to 1MHz using the factory-stored 1MHz calibration values.

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