The Time of Day (TOD) Clock in a 171CBB97030 Processor May be Incorrect After Being Powered Down



Release Notice

The purpose of this resolution is to inform 171CBB97030 users of a possible Time of Day (TOD) clock issue.

Goals and Symptoms

An issue has been found with the TOD clock in 171CBB97030 modules. If the TOD clock feature is configured and the 171CBB97030 is powered down, the TOD clock may contain the incorrect time and/or date after the assembly is powered up. In most conditions, the clock time at power up will be incorrect by the amount of time the unit was powered down. In addition to the incorrect time, other TOD fault conditions may also include an incorrect Day of the Week or Year after power up.

* Refer to the 'Facts and Changes' section in this document to determine if a TOD problem exists.

Facts and Changes

This resolution affects the following PRODUCTS with the PV number and the 'Date of Manufacture' (DOM):

Part Number
PV number
Date of Manufacter (DOM)
PV02 to PV05
from May 2007
  • It is not possible to determine which modules within the PV and 'Date of Manufacture' (DOM) range may exhibit the TOD issue unless a power cycle test is performed.
  • How to determine if the TOD clock is functioning normally in a system. (This test is valid only if a TOD clock is configured and a working battery is installed)
    Powering down the CBB processor/switch will be necessary to perform this test. Please check with the proper personnel when it is acceptable to perform this test.

    1. To begin, verify the current Time and Date in the PLC by going online and recording the clock time and date. Once this is recorded, disconnect from online.
    2. Next, power down the PLC for approximately 3-4 minutes.
    3. Power up the PLC and connect online. Verify that the Time and Date are still in the expected range of the PC clock.
    4. If the Time and Date results are correct, then no further action is required.
    5. If the Time and Date results are incorrect by the amount of time the assembly was powered down, then it is recommended that the 171CBB97030 be exchanged.
  • If an exchange is necessary, reference the Quality Information document IQ102452 when ordering.

Causes and Fixes

It has been determined that the TOD clock processor code was incorrectly installed in some instances. New code is now available in the new TOD clock processors that prevents this situation from reoccurring. Since this code is not field upgradeable, any adapter matching the PV number and DOM above and exhibiting the symptoms described must be exchanged.

The following PV numbers identify new or updated adapters:

Part Number
PV number
Date of Manufacter (DOM)
PV06 or higher
does not apply

Legacy KB System (APS) Data: RESL203508 V1.0, Originally authored by DaDz on 09/23/2010, Last Edited by DaDz on 09/23/2010
Related ranges: Modicon Momentum