MCP7940N Errata Datasheet by Microchip Technology

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‘ Mlcgcmp MC P7940 N :
2014-2018 Microchip Technology Inc. DS80000611D-page 1
MCP7940N
The MCP7940N family devices that you have received
conform functionally to the current Device Data Sheet
(DS20005010G), except for the anomalies described in
this document.
The silicon issues discussed in the following pages are
for devices listed in Table 1. The silicon issues are
summarized in Table 2.
The errata described in this document will be addressed
in future revisions of the MCP7940N silicon.
Note: This document summarizes all silicon
errata issues from all revisions of silicon,
previous as well as current. Only the
issues indicated in the last column of
Table 2 apply to the current silicon
revision.
Note: For more information on identifying the
product date code, refer to Packaging
Information section of the product Data
Sheet or contact your local Microchip
sales office.
TABLE 1: AFFECTED PART NUMBERS
Part Number
MCP7940N
TABLE 2: SILICON ISSUE SUMMARY
Issue Number Issue Summary Affected Date Codes(1, 2)
All
1 Date incrementing at noon. X
2 Spurious alarm interrupts when matching on minutes. X
3 Date value changing on month write. X
4 Day of week register value changing after write. X
Note 1: Only those issues indicated in the last column apply to the current silicon revision.
2: The date codes are presented in YYWW format.
MCP7940N Family Silicon Errata
Work around Allecled Silicon Revisions Work around Work around Allecled Silicon Revisions E Work around Allecled Silicon Revisions E
2014-2018 Microchip Technology Inc. DS80000611D-page 2
MCP7940N
Silicon Errata Issues
1. Issue: Date Increment
When operating in 12-hour mode
(RTCHOUR<6> is set) if the application loads
an hour value before 12:00 PM while the oscilla-
tor is running then the date and day of week may
increment at 12:00 PM. When this occurs, the
month and year will also increment according to
the normal rollover rules. The date will incre-
ment again at 12:00 AM.
Work around
Disable the oscillator by ensuring both the ST
and EXTOSC bits are cleared and wait for the
OSCRUN bit to clear before loading the new
hour value.
Affected Silicon Revisions
2. Issue: Spurious Minute-Match Alarm
Interrupts
When using an alarm to match on minutes
(ALMxMSK<2:0> = 001) and digital trimming is
being used to slow down the time
(TRIMVAL<6:0> > 0 and SIGN = 0), spurious
alarm interrupts may occur at incorrect minutes.
Work around
When an alarm interrupt occurs, read the
RTCMIN register and confirm the minute
matches the desired value for the alarm.
Affected Silicon Revisions
3. Issue: Date Value Changing on Month
Write
When writing a different value to the month
register, RTCMTH (0x05), the value of the date
register, RTCDATE (0x04), may change.
Work around
After writing to the RTCMTH register, verify the
RTCDATE value is correct or write the correct
RTCDATE value again.
Affected Silicon Revisions
4. Issue: Day of Week Value Changing
After Write
If the RTCWKDAY register is written while the
oscillator is stopped, it is possible that the value
will read back as a different value after the
oscillator is started.
Work around
After writing to the RTCWKDAY register, read
the value back after the oscillator is started to
confirm it is correct and, if necessary, rewrite it.
Affected Silicon Revisions
Note: This document summarizes all silicon
errata issues from all revisions of silicon,
previous as well as current. Only the
issues indicated by the shaded column in
the following tables apply to the current
silicon revision.
All
X
All
X
All
X
All
X
Rev A Docu ment (04/2014) Rev B Document (12/2015) Rev C Document (02/2013) Rev D Document (10/2013)
2014-2018 Microchip Technology Inc. DS80000611D-page 3
MCP7940N
APPENDIX A: DOCUMENT
REVISION HISTORY
Rev A Document (04/2014)
Initial release of this document.
Rev B Document (12/2015)
Added Silicon Issue 2 (spurious alarm interrupts when
matching on minutes).
Rev C Document (02/2018)
Added Silicon Issue 3 (date value changing on month
write).
Rev D Document (10/2018)
Added Silicon Issue 4 (day of week register value
changing after write).
YSTEM
2014-2018 Microchip Technology Inc. DS80000611D-page 4
MCP7940N
Information contained in this publication regarding device
applications and the like is provided only for your convenience
and may be superseded by updates. It is your responsibility to
ensure that your application meets with your specifications.
MICROCHIP MAKES NO REPRESENTATIONS OR
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OTHERWISE, RELATED TO THE INFORMATION,
INCLUDING BUT NOT LIMITED TO ITS CONDITION,
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FITNESS FOR PURPOSE. Microchip disclaims all liability
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Trademarks
The Microchip name and logo, the Microchip logo, AnyRate, AVR,
AVR logo, AVR Freaks, BitCloud, chipKIT, chipKIT logo,
CryptoMemory, CryptoRF, dsPIC, FlashFlex, flexPWR, Heldo,
JukeBlox, KeeLoq, Kleer, LANCheck, LINK MD, maXStylus,
maXTouch, MediaLB, megaAVR, MOST, MOST logo, MPLAB,
OptoLyzer, PIC, picoPower, PICSTART, PIC32 logo, Prochip
Designer, QTouch, SAM-BA, SpyNIC, SST, SST Logo,
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motorBench, MPASM, MPF, MPLAB Certified logo, MPLIB,
MPLINK, MultiTRAK, NetDetach, Omniscient Code Generation,
PICDEM, PICDEM.net, PICkit, PICtail, PowerSmart, PureSilicon,
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All other trademarks mentioned herein are property of their
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© 2018, Microchip Technology Incorporated, All Rights Reserved.
ISBN: 978-1-5224-3595-2
Note the following details of the code protection feature on Microchip devices:
Microchip products meet the specification contained in their particular Microchip Data Sheet.
Microchip believes that its family of products is one of the most secure families of its kind on the market today, when used in the
intended manner and under normal conditions.
There are dishonest and possibly illegal methods used to breach the code protection feature. All of these methods, to our
knowledge, require using the Microchip products in a manner outside the operating specifications contained in Microchip’s Data
Sheets. Most likely, the person doing so is engaged in theft of intellectual property.
Microchip is willing to work with the customer who is concerned about the integrity of their code.
Neither Microchip nor any other semiconductor manufacturer can guarantee the security of their code. Code protection does not
mean that we are guaranteeing the product as “unbreakable.”
Code protection is constantly evolving. We at Microchip are committed to continuously improving the code protection features of our
products. Attempts to break Microchip’s code protection feature may be a violation of the Digital Millennium Copyright Act. If such acts
allow unauthorized access to your software or other copyrighted work, you may have a right to sue for relief under that Act.
Microchip received ISO/TS-16949:2009 certification for its worldwide
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and India. The Company’s quality system processes and procedures
are for its PIC® MCUs and dsPIC® DSCs, KEELOQ® code hopping
devices, Serial EEPROMs, microperipherals, nonvolatile memory and
analog products. In addition, Microchip’s quality system for the design
and manufacture of development systems is ISO 9001:2000 certified.
QUALITYMANAGEMENTS
YSTEM
CERTIFIEDBYDNV
== ISO/TS16949==
6‘ MICROCHIP
2014-2018 Microchip Technology Inc. DS80000611D-page 5
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