USCI41
USCI Module
Category
Functional
Function
UCBUSY bit of eUSCIA module might not work reliable when device is in SPI mode.
Description
When eUSCIA is configured in SPI mode, the UCBUSY bit might get stuck to 1 or start
toggling after transmission is completed. This happens in all four combinations of Clock
Phase and Clock Polarity options (UCAxCTLW0.UCCKPH & UCAxCTLW0.UCCKPL bits)
as well as in Master and Slave mode. There is no data loss or corruption. However the
UCBUSY cannot be used in its intended function to check if transmission is completed.
Because the UCBUSY bit is stuck to 1 or toggles, the clock request stays enabled and
this adds additional current consumption in low power mode operation.
Workaround
For correct functional implementation check on transmit or receive interrupt flag
UCTXIFG/UCRXIFG instead of UCBUSY to know if the UCAxTXBUF buffer is empty or
ready for the next complete character.
To reduce the additional current it is recommended to either reset the SPI module
(UCAxCTLW0.UCSWRST) in the UCBxCTLW0 or send a dummy byte 0x00 after the
intended SPI transmission is completed.
USCI42
USCI Module
Category
Functional
Function
UART asserts UCTXCPTIFG after each byte in multi-byte transmission
Description
UCTXCPTIFG flag is triggered at the last stop bit of every UART byte transmission,
independently of an empty buffer, when transmitting multiple byte sequences via UART.
The erroneous UART behavior occurs with and without DMA transfer.
Workaround
None.
USCI47
USCI Module
Category
Functional
Function
eUSCI SPI slave with clock phase UCCKPH = 1
Description
The eUSCI SPI operates incorrectly under the following conditions:
1. The eUSCI_A or eUSCI_B module is configured as a SPI slave with clock phase mode
UCCKPH = 1
AND
2. The SPI clock pin is not at the appropriate idle level (low for UCCKPL = 0, high for
UCCKPL = 1) when the UCSWRST bit in the UCxxCTLW0 register is cleared.
If both of the above conditions are satisfied, then the following will occur:
eUSCI_A: the SPI will not be able to receive a byte (UCAxRXBUF will not be filled and
UCRXIFG will not be set) and SPI slave output data will be wrong (first bit will be missed
and data will be shifted).
eUSCI_B: the SPI receives data correctly but the SPI slave output data will be wrong (first
byte will be duplicated or replaced by second byte).
Workaround
Use clock phase mode UCCKPH = 0 for MSP SPI slave if allowed by the application.
Advisory Descriptions
24
MSP430F6747 Microcontroller
SLAZ486AD – DECEMBER 2012 – REVISED MAY 2021
Copyright © 2021 Texas Instruments Incorporated
