SLAZ098AA October   2012  – May 2021 CC430F6125

 

  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.      RGC64
    3. 5.3 Memory-Mapped Hardware Revision (TLV Structure)
  6. 6Advisory Descriptions
    1. 6.1  AES1
    2. 6.2  BSL7
    3. 6.3  COMP4
    4. 6.4  COMP10
    5. 6.5  CPU18
    6. 6.6  CPU20
    7. 6.7  CPU21
    8. 6.8  CPU22
    9. 6.9  CPU23
    10. 6.10 CPU24
    11. 6.11 CPU25
    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 CPU39
    23. 6.23 CPU40
    24. 6.24 CPU46
    25. 6.25 CPU47
    26. 6.26 DMA4
    27. 6.27 DMA7
    28. 6.28 DMA8
    29. 6.29 DMA10
    30. 6.30 EEM8
    31. 6.31 EEM9
    32. 6.32 EEM11
    33. 6.33 EEM13
    34. 6.34 EEM14
    35. 6.35 EEM16
    36. 6.36 EEM17
    37. 6.37 EEM19
    38. 6.38 EEM23
    39. 6.39 FLASH29
    40. 6.40 FLASH31
    41. 6.41 FLASH37
    42. 6.42 JTAG20
    43. 6.43 JTAG26
    44. 6.44 JTAG27
    45. 6.45 LCDB1
    46. 6.46 LCDB3
    47. 6.47 LCDB4
    48. 6.48 LCDB5
    49. 6.49 LCDB6
    50. 6.50 MPY1
    51. 6.51 PMAP1
    52. 6.52 PMM8
    53. 6.53 PMM9
    54. 6.54 PMM10
    55. 6.55 PMM11
    56. 6.56 PMM12
    57. 6.57 PMM14
    58. 6.58 PMM15
    59. 6.59 PMM17
    60. 6.60 PMM18
    61. 6.61 PMM20
    62. 6.62 PORT15
    63. 6.63 PORT16
    64. 6.64 PORT17
    65. 6.65 PORT19
    66. 6.66 PORT21
    67. 6.67 RF1A1
    68. 6.68 RF1A2
    69. 6.69 RF1A3
    70. 6.70 RF1A5
    71. 6.71 RF1A6
    72. 6.72 RF1A8
    73. 6.73 RTC3
    74. 6.74 RTC6
    75. 6.75 SYS16
    76. 6.76 TAB23
    77. 6.77 UCS6
    78. 6.78 UCS7
    79. 6.79 UCS9
    80. 6.80 UCS10
    81. 6.81 UCS11
    82. 6.82 USCI26
    83. 6.83 USCI30
    84. 6.84 USCI31
    85. 6.85 USCI34
    86. 6.86 USCI35
    87. 6.87 USCI39
    88. 6.88 USCI40
    89. 6.89 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