SPRZ447E July   2017  – July 2024 AM5746 , AM5748 , AM5749

 

  1.   1
  2. 1Introduction
    1.     Related Documentation
    2.     Trademarks
    3.     Modules Impacted
  3. 2Silicon Advisories
    1.     Revisions SR 1.0 - Advisories List
    2.     i202
    3.     i378
    4.     i631
    5.     i694
    6.     i698
    7.     i699
    8.     i709
    9.     i727
    10.     i729
    11.     i734
    12.     i767
    13.     i782
    14.     i783
    15.     i802
    16.     i803
    17.     i807
    18.     i808
    19.     i809
    20.     i810
    21.     i813
    22.     i814
    23.     i815
    24.     i818
    25.     i819
    26.     i820
    27.     i824
    28.     i826
    29.     i829
    30.     i834
    31.     i849
    32.     i856
    33.     i862
    34.     i863
    35.     i869
    36.     i870
    37.     i871
    38.     i872
    39.     i874
    40.     i878
    41.     i879
    42.     i883
    43.     i889
    44.     i890
    45.     i893
    46.     i896
    47.     i897
    48.     i898
    49.     i899
    50.     i900
    51.     i903
    52.     i904
    53.     i916
    54.     i929
    55.     i930
    56.     i932
    57.     i933
    58.     i936
    59.     i940
    60.     i2446
  4. 3Silicon Limitations
    1.     Revisions SR 1.0 - Limitations List
    2.     i596
    3.     i641
    4.     i833
    5.     i838
    6.     i845
    7.     i848
    8.     i876
    9.     i877
    10.     i892
    11.     i909
    12.     i925
  5. 4Silicon Cautions
    1.     Revisions SR 1.0 - Cautions List
    2.     i827
    3.     i832
    4.     i836
    5.     i839
    6.     i864
    7.     i885
    8.     i886
    9.     i912
    10.     i926
    11.     i931
    12.     i935
    13.     i937
  6. 5Revision History

i916

QSPI Reads Can Fail For Flash Devices with HOLD Function

CRITICALITY

High

DESCRIPTION

The default internal pull-up/pull-down on the SoC QSPI interface can interfere with the HOLD function implemented in some QSPI FLASH devices leading to Read Failures. This is most likely to be seen at higher clock rates, and with EDMA reads of greater than 128-Bytes.

In Quad SPI mode, the SoC QSPI IP transmits the command and address to the flash device on data line D0 and reads the data back on all four data lines D0, D1, D2 and D3. The default values of the data lines i.e. values when there is no driver on lines are LOW for D0 and D1 and HIGH for D2 and D3. These values are dictated by the internal and external pull ups.

When the last bit on the last read driven by the FLASH doesn't match the 'default value', the data lines D1, D2 and D3 transition slowly to their default values i.e. LOW for D1 and HIGH for D2 and D3. The transition time is in the order of 100 ns and depends on board loadings. At higher frequencies (typically above 64MHz QSPI clock rate) the time from the last bit of data transfer to the first bit of the next command is not long enough to allow for the pull-ups to get the data lines D1, D2 and D3 to the desired state. It is possible that the D3 line is still in a LOW state when the next command transmission begins.

The D3 line is used by some flash devices as a HOLD signal. If the D3 line has not reached HIGH state by the time CS is reasserted, flash devices can infer that a HOLD is in effect and fail to service the current command.

This issue is most easily seen with EDMA reads of length greater than 128 bytes. CPU reads typically provide sufficient time between reads for the data lines to reach their default values.

WORKAROUND

The software workaround is to disable the hold functionality on the QSPI device, preferably by setting a nonvolatile configuration register. On most flash devices, placing the QSPI device in Quad read mode automatically disables the HOLD functionality. On certain flash devices, there is a separate mode bit that can be set to disable the HOLD functionality. Typically this setting would be done in a Flash Writer utility that programs the flash with the customer’s boot image and sets appropriate non-volatile mode bits. Depending on the software architecture, this mode bit setting may also be done in the boot-loader or HLOS kernel.

Disabling the HOLD functionality prevents the slow ramp on the D3 line from interrupting the operation of the QSPI flash device and allows EDMA reads at high clock speeds (64 MHz).

There are no negative effects of the workaround as HOLD functionality is not supported by SoC QSPI IP.

REVISIONS IMPACTED

AM574x SR 1.0
AM576x SR 1.0

AM574x: 1.0

DRA75xP, DRA74xP, DRA77xP, DRA76xP: 1.0

TDA2Px: 1.0

AM576x: 1.0