SLAZ094AB October   2012  – May 2021 CC430F5137

 

  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.      RGZ48
    3. 5.3 Memory-Mapped Hardware Revision (TLV Structure)
  6. 6Advisory Descriptions
    1. 6.1  ADC24
    2. 6.2  ADC25
    3. 6.3  ADC27
    4. 6.4  ADC29
    5. 6.5  ADC42
    6. 6.6  ADC69
    7. 6.7  AES1
    8. 6.8  BSL7
    9. 6.9  COMP4
    10. 6.10 COMP10
    11. 6.11 CPU18
    12. 6.12 CPU20
    13. 6.13 CPU21
    14. 6.14 CPU22
    15. 6.15 CPU23
    16. 6.16 CPU24
    17. 6.17 CPU25
    18. 6.18 CPU26
    19. 6.19 CPU27
    20. 6.20 CPU28
    21. 6.21 CPU29
    22. 6.22 CPU30
    23. 6.23 CPU31
    24. 6.24 CPU32
    25. 6.25 CPU33
    26. 6.26 CPU34
    27. 6.27 CPU35
    28. 6.28 CPU39
    29. 6.29 CPU40
    30. 6.30 CPU46
    31. 6.31 CPU47
    32. 6.32 DMA4
    33. 6.33 DMA7
    34. 6.34 DMA8
    35. 6.35 DMA10
    36. 6.36 EEM8
    37. 6.37 EEM9
    38. 6.38 EEM11
    39. 6.39 EEM13
    40. 6.40 EEM14
    41. 6.41 EEM16
    42. 6.42 EEM17
    43. 6.43 EEM19
    44. 6.44 EEM23
    45. 6.45 FLASH29
    46. 6.46 FLASH31
    47. 6.47 FLASH37
    48. 6.48 JTAG20
    49. 6.49 JTAG26
    50. 6.50 JTAG27
    51. 6.51 MPY1
    52. 6.52 PMAP1
    53. 6.53 PMM8
    54. 6.54 PMM9
    55. 6.55 PMM10
    56. 6.56 PMM11
    57. 6.57 PMM12
    58. 6.58 PMM14
    59. 6.59 PMM15
    60. 6.60 PMM17
    61. 6.61 PMM18
    62. 6.62 PMM20
    63. 6.63 PORT15
    64. 6.64 PORT16
    65. 6.65 PORT17
    66. 6.66 PORT19
    67. 6.67 PORT21
    68. 6.68 RF1A1
    69. 6.69 RF1A2
    70. 6.70 RF1A3
    71. 6.71 RF1A5
    72. 6.72 RF1A6
    73. 6.73 RF1A8
    74. 6.74 RTC3
    75. 6.75 RTC6
    76. 6.76 SYS16
    77. 6.77 TAB23
    78. 6.78 UCS6
    79. 6.79 UCS7
    80. 6.80 UCS9
    81. 6.81 UCS10
    82. 6.82 UCS11
    83. 6.83 USCI26
    84. 6.84 USCI30
    85. 6.85 USCI31
    86. 6.86 USCI34
    87. 6.87 USCI35
    88. 6.88 USCI39
    89. 6.89 USCI40
    90. 6.90 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