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State of FLASHCONF register at TM4C1294NCPDT reset disagrees with datasheet

Chester Gillon
Guru 92251 points
Other Parts Discussed in Thread: TM4C1294NCPDT

According to the TivaTM TM4C1294NCPDT Microcontroller Datasheet SPMS433A, the state of Flash Configuration Register (FLASHCONF) after reset should be:

- FPFON = 1
- FPFOFF = 0

However, with a XM4C1294NCPDT with the processor halted at the reset vector (after a System Reset) the FLASHCONF register is showing both FPFON = 0 and FPFOFF = 0

The device identification registers are:

SYSCTL_DID0 = 0x100A0001
SYSCTL_DID1 = 0x101FC06D

My questions are:
1) If the FPFON and FPFOFF bits are both zero, does it mean that the flash pre-fetch buffer is on or off?

2) Since the state of FPFON at reset differs between the device (FPFON = 0) and the datasheet (FPFON = 1) is this an error in the datasheet, or a device errata?

  • 0
    TI__Guru**** 244380 points

    Hello Chester.

    The default value of the register in the data sheet is up for correction. The next release of datasheets would fix the same.

    The FPFON and FPFOFF are to be used for SW control. By default when using a higher frequency the Flash Prefetch is switched ON automatically. If the SW requires to keep the Flash prefetch Buffer ON for lower frequency then the FPFON must be set to override the automatic settings in TM4C129.

    The FPFOFF bit is given as a diagnostic bit for SW Testing.

    Regards

    Amit

  • 0 in reply to Amit Ashara
    Guru 92251 points

    Amit Ashara said:
    The FPFOFF bit is given as a diagnostic bit for SW Testing.

    Thanks for the information.

    The only reason I was looking at the FPFOFF and FPFON bits is because http://processors.wiki.ti.com/index.php/TI-RTOS_TM4C129_Emac_Issues details some TI-RTOS driver changes which make use of those bits, and I was trying to determine if either:

    a) The TI-RTOS driver changes were working-around a TM4C129 EMAC errata in the chip.

    b) The TI-RTOS driver for the TM4C129 has "race conditions" such that slowing down the code (by disabling the flash pre-fetch) make the initialization "work".

  • 0 in reply to Chester Gillon
    TI__Guru**** 244380 points

    Hello Chester.

    The TI-RTOS driver change is to work around the errata, while we find the root-cause.

    Regards

    Amit