SLAZ269AB October   2012  – May 2021 MSP430F5325

 

  1. 1Functional Advisories
  2. 2Preprogrammed Software Advisories
  3. 3Debug Only Advisories
  4. 4Fixed by Compiler Advisories
  5. 5Nomenclature, Package Symbolization, and Revision Identification
    1. 5.1 Device Nomenclature
    2. 5.2 Package Markings
      1.      PN80
    3. 5.3 Memory-Mapped Hardware Revision (TLV Structure)
  6. 6Advisory Descriptions
    1. 6.1  ADC25
    2. 6.2  ADC27
    3. 6.3  ADC29
    4. 6.4  ADC42
    5. 6.5  ADC69
    6. 6.6  BSL6
    7. 6.7  BSL7
    8. 6.8  COMP10
    9. 6.9  CPU21
    10. 6.10 CPU22
    11. 6.11 CPU23
    12. 6.12 CPU26
    13. 6.13 CPU27
    14. 6.14 CPU28
    15. 6.15 CPU29
    16. 6.16 CPU30
    17. 6.17 CPU31
    18. 6.18 CPU32
    19. 6.19 CPU33
    20. 6.20 CPU34
    21. 6.21 CPU35
    22. 6.22 CPU37
    23. 6.23 CPU39
    24. 6.24 CPU40
    25. 6.25 CPU47
    26. 6.26 DMA4
    27. 6.27 DMA7
    28. 6.28 DMA8
    29. 6.29 DMA10
    30. 6.30 EEM9
    31. 6.31 EEM11
    32. 6.32 EEM13
    33. 6.33 EEM14
    34. 6.34 EEM15
    35. 6.35 EEM16
    36. 6.36 EEM17
    37. 6.37 EEM19
    38. 6.38 EEM21
    39. 6.39 EEM23
    40. 6.40 FLASH33
    41. 6.41 FLASH34
    42. 6.42 FLASH35
    43. 6.43 FLASH37
    44. 6.44 JTAG20
    45. 6.45 JTAG26
    46. 6.46 JTAG27
    47. 6.47 LDO1
    48. 6.48 MPY1
    49. 6.49 PMAP1
    50. 6.50 PMM9
    51. 6.51 PMM10
    52. 6.52 PMM11
    53. 6.53 PMM12
    54. 6.54 PMM14
    55. 6.55 PMM15
    56. 6.56 PMM17
    57. 6.57 PMM18
    58. 6.58 PMM20
    59. 6.59 PORT15
    60. 6.60 PORT16
    61. 6.61 PORT19
    62. 6.62 PORT24
    63. 6.63 RTC3
    64. 6.64 RTC6
    65. 6.65 SYS10
    66. 6.66 SYS12
    67. 6.67 SYS14
    68. 6.68 SYS16
    69. 6.69 TAB23
    70. 6.70 USCI26
    71. 6.71 USCI30
    72. 6.72 USCI31
    73. 6.73 USCI34
    74. 6.74 USCI35
    75. 6.75 USCI39
    76. 6.76 USCI40
    77. 6.77 WDG4
  7. 7Revision History

USCI30

USCI Module

Category

Functional

Function

I2C mode master receiver / slave receiver

Description

When the USCI I2C module is configured as a receiver (master or slave), it performs a double-buffered receive operation. In a transaction of two bytes, once the first byte is moved from the receive shift register to the receive buffer the byte is acknowledged and the state machine allows the reception of the next byte.

If the receive buffer has not been cleared of its contents by reading the UCBxRXBUF register while the 7th bit of the following data byte is being received, an error condition may occur on the I2C bus. Depending on the USCI configuration the following may occur:

1) If the USCI is configured as an I2C master receiver, an unintentional repeated start condition can be triggered or the master switches into an idle state (I2C communication aborted). The reception of the current data byte is not successful in this case.
2) If the USCI is configured as I2C slave receiver, the slave can switch to an idle state stalling I2C communication. The reception of the current data byte is not successful in this case. The USCI I2C state machine will notify the master of the aborted reception with a NACK.

Note that the error condition described above occurs only within a limited window of the 7th bit of the current byte being received. If the receive buffer is read outside of this window (before or after), then the error condition will not occur.

Workaround

a) The error condition can be avoided altogether by servicing the UCBxRXIFG in a timely manner. This can be done by (a) servicing the interrupt and ensuring UCBxRXBUF is read promptly or (b) Using the DMA to automatically read bytes from receive buffer upon UCBxRXIFG being set.

OR

b) In case the receive buffer cannot be read out in time, test the I2C clock line before the UCBxRXBUF is read out to ensure that the critical window has elapsed. This is done by checking if the clock line low status indicator bit UCSCLLOW is set for atleast three USCI bit clock cycles i.e. 3 X t(BitClock).

Note that the last byte of the transaction must be read directly from UCBxRXBUF. For all other bytes follow the workaround:

Code flow for workaround

(1) Enter RX ISR for reading receiving bytes
(2) Check if UCSCLLOW.UCBxSTAT == 1
(3) If no, repeat step 2 until set
(4) If yes, repeat step 2 for a time period > 3 x t (BitClock) where t (BitClock) = 1/ f (BitClock)
(5) If window of 3 x t(BitClock) cycles has elapsed, it is safe to read UCBxRXBUF