SLAZ542T July   2013  – May 2021 MSP430F5234

 

  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  BSL7
    2. 6.2  COMP10
    3. 6.3  CPU21
    4. 6.4  CPU22
    5. 6.5  CPU40
    6. 6.6  CPU47
    7. 6.7  DMA4
    8. 6.8  DMA7
    9. 6.9  DMA10
    10. 6.10 EEM17
    11. 6.11 EEM19
    12. 6.12 EEM21
    13. 6.13 EEM23
    14. 6.14 JTAG26
    15. 6.15 JTAG27
    16. 6.16 PMAP1
    17. 6.17 PMM9
    18. 6.18 PMM11
    19. 6.19 PMM12
    20. 6.20 PMM14
    21. 6.21 PMM15
    22. 6.22 PMM18
    23. 6.23 PMM20
    24. 6.24 PORT15
    25. 6.25 PORT19
    26. 6.26 PORT33
    27. 6.27 RTC3
    28. 6.28 RTC6
    29. 6.29 SYS12
    30. 6.30 SYS16
    31. 6.31 UCS7
    32. 6.32 UCS9
    33. 6.33 UCS11
    34. 6.34 USCI26
    35. 6.35 USCI34
    36. 6.36 USCI35
    37. 6.37 USCI39
    38. 6.38 USCI40
  7. 7Revision History

UCS7

UCS Module

Category

Functional

Function

DCO drifts when servicing short ISRs when in LPM0 or exiting active from ISRs for short periods of time

Description

The FLL uses two rising edges of the reference clock to compare against the DCO frequency and decide on the required modifications to the DCOx and MODx bits. If the device is in a low power mode with FLL disabled (LPM0 with DCO not sourcing ACLK/SMCLK or LPM2, LPM3, LPM4 where SCG1 bit is set) and enters a state which enables FLL (enter ISR from LPM0/LPM2 or exit active from ISRs) for a period less than 3x reference clock cycles, then the FLL will cause the DCO to drift.
This occurs because the FLL immediately begins comparing an active DCO with its reference clock and making the respective modifications to the DCOx and MODx bits. If the FLL is not given sufficient time to capture a full reference clock cycle (2 x reference clock periods) and adjust accordingly (1 x reference clock period), then the DCO will keep drifting each time the FLL is enabled.

Workaround

(1) If DCO is not sourcing ACLK or SMCLK in the application, use LPM1 instead of LPM0 to make sure FLL is disabled when interrupt service routine is serviced.
(2) When exiting active from ISRs, insert a delay of at least 3 x reference clock periods. To save on power budget, the 3 x reference clock periods could also be spent in LPM0 with TimerA or TimerB using ACLK/SMCLK sourced from DCO. This way, the FLL and DCO are still active in LPM0.