MSP430I2021: How to set UCBRSx

O.H

Genius 5340 points

Part Number: MSP430I2021

Hi experts,

Let me check the setting of the EUSCI register (UCBRSx) in the following system.

SMCLK = 16.384MHz/4 = 4.096MHz
N=4.096MHz/38400bps = 106.6666...

In the above case, which is correct?

Rounding up the decimal point: UCBRSx=D6h
Rounding down the decimal point: UCBRSx=B6h

By the way, in the simulator below, "UCBRSx=B6h" was used.

MSP430 USCI/EUSCI UART Baud Rate Calculation
:software-dl.ti.com/.../index.html

Best regards,
O.H

over 2 years ago

0 James Evans over 2 years ago

TI__Mastermind 49692 points

Hello,

N-INT(N) = 0.66667 which is the fractional part of N. Looking at Table 10-4, I see 0.6667 which is nearly the exact number, so I would use UCBRSx = 0xD6.

0 O.H over 2 years ago in reply to James Evans

Genius 5340 points

Hello,

Thank you for your answer. In this case, I will use UCBRSx = 0xD6.

By the way, the simulator uses UCBRSx = 0xB6. Is it correct to assume that the simulator's calculation algorithm truncates the fifth decimal place? Just to be sure.

Best regards,
O.H

0 James Evans over 2 years ago in reply to O.H

TI__Mastermind 49692 points

The calculator's algorithm may select UCBRSx by rounding down (e.g. flooring) the fractional part of N. The calculator is a good, quick reference for getting started, and the UART communication will probably work fine in most cases. However, it is always wise to double-check the settings by performing these calculations manually.

0 O.H over 2 years ago in reply to James Evans

Genius 5340 points

I understood.

Thank you for your kind support!

Best regards,
O.H

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MSP430I2021: How to set UCBRSx