MCP795WXX
MCP795WXX Family Silicon Errata
The MCP795WXX family devices that you have
received conform functionally to the current Device
Data Sheet (DS20002280D), 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 MCP795WXX 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.
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
MCP795W10
MCP795W11
MCP795W12
MCP795W20
MCP795W21
MCP795W22
Note:
TABLE 2:
SILICON ISSUE SUMMARY
Affected Date Codes
(1,
2)
Issue Summary
All
Time running fast when V
CC
> 3.6V.
Incorrect square wave clock output frequency when V
CC
> 3.6V.
Incorrect EVLS debounce period when V
CC
> 3.6V.
Incorrect WDT time-out period and pulse width when V
CC
> 3.6V.
Incorrect alarm interrupt output pulse width when using the WDO
pin and V
CC
> 3.6V.
Date incrementing at noon.
Month write changing date value.
Day of week write resetting to 1.
Hundredth-second out of sync with second.
Hundredth of Second value not changing.
Only those issues indicated in the last column apply to the current silicon revision.
The date codes are presented in YYWW format.
X
X
X
X
X
X
X
X
X
X
Issue Number
1
2
3
4
5
6
7
8
9
10
Note 1:
2:
2012-2017 Microchip Technology Inc.
DS80000542D-page 1
MCP795WXX
Silicon Errata Issues
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.
4. Issue:
Incorrect WDT Timings
When V
CC
is greater than 3.6V, the Watchdog
Timer time-out period and output pulse width will
not match the data sheet-specified values.
Work around
Operate the device at or below 3.6V.
Affected Silicon Revisions
1. Issue:
Time Running Fast
All
X
When V
CC
is greater than 3.6V, the internal time
keeping registers do not count correctly,
resulting in fast operation.
Work around
Operate the device at or below 3.6V.
Affected Silicon Revisions
All
X
5. Issue:
Incorrect Alarm Output Pulse
Width
When V
CC
is greater than 3.6V, if the WDO pin
is selected as the alarm interrupt output pin, the
output pulse width will not match the data sheet-
specified value.
Work around
Operate the device at or below 3.6V.
Affected Silicon Revisions
All
X
2. Issue:
Incorrect Clock Output
Frequency
When Vcc is greater than 3.6V, selecting a
square wave frequency for the CLKOUT pin
other than 32.768 kHz will result in the incorrect
frequency being outputted.
Work around
Operate the device at or below 3.6V or select
32.768 kHz output.
Affected Silicon Revisions
All
X
6. 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
oscillator 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 increment again at 12:00 AM.
Work around
Disable the oscillator by ensuring both the ST
and EXTOSC bits are cleared and wait for the
OSCON bit to clear before loading the new hour
value.
Affected Silicon Revisions
All
X
3. Issue:
Incorrect EVLS Debounce
Timing
When V
CC
is greater than 3.6V, the low-speed
event detect debounce period will not match the
data sheet-specified values.
Work around
Operate the device at or below 3.6V.
Affected Silicon Revisions
All
X
DS80000542D-page 2
2012-2017 Microchip Technology Inc.
MCP795WXX
7. Issue:
Date Reset after Month Write
9. Issue:
If the application writes a new month value to the
timekeeping registers, some combinations of
date and month values may result in the date
being reset to 1 or 21, even if the date is also
written with the month.
Work around
Disable the oscillator by clearing the ST bit, and
wait for the OSCON bit to clear. Write new
Month value as a separate Write command.
Then, write the new valid Date value as a
separate Write command. Write the Month value
again. Then, restart the oscillator and wait until
the clock starts or monitor the OSCON bit until it
is set. For the special case of February 29, first
ensure that the year is a leap year and that the
LY bit is set.
Affected Silicon Revisions
All
X
HSEC Value Not Synchronized
with Second Value
When reading the HSEC register and Second
register shortly after the time values are set, the
two registers may not roll over at the same
moment.
Work around
The HSEC register does not cause the Second
value to change, but instead the values are
clocked off an internal clock divisor inde-
pendently. The HSEC value is automatically
synchronized with the Second value at the
beginning of the minute, when the second rolls
over from 59 to 00. Following that first minute
change, the HSEC and Second registers will be
in sync.
Affected Silicon Revisions
All
X
10. Issue:
8. Issue:
Day of Week Reset after Day of
Week Write
HSEC Value Not Changing
If the day of week (RTCWKDAY<2:0>) is equal
to the value of 7 and the application writes a new
day of week value to the timekeeping registers
while the oscillator is not running, then when the
oscillator is enabled, the day of week may reset
the value to 1.
Work around
Update the day of week while the oscillator is
enabled. Or, change the day of week value to
another value besides 7 before disabling the
oscillator, then set to the correct day while the
oscillator is disabled, before re-enabling the
oscillator.
Affected Silicon Revisions
All
X
The HSEC register may appear stuck at the
same value for two or more successive reads,
even though more than 10 ms have passed. If
the oscillator is running, then the internal value
is still counting, but the value may not be
updated every time it is read.
Work around
Read the HSEC value, then read it again 120 µs
later to ensure an unstuck value. Alternatively,
read the HSEC register and compare the
present value with the previous value, and if the
same, re-read the HSEC register until it is
different.
2012-2017 Microchip Technology Inc.
DS80000542D-page 3
MCP795WXX
APPENDIX A:
DOCUMENT
REVISION HISTORY
Rev A Document (03/2012)
Initial release of this document.
Rev B Document (12/2015)
Adopted new document format. Added silicon issues 6
(date incrementing at noon) and 7 (month write reset-
ting date to 1). Removed MCP795BXX part numbers.
Rev C Document (12/2016)
Added Issue 8: Day of Week Reset after Day of Week
Write.
Rev D Document (06/2017)
Edited Issue 7; Added Issues 9 and 10.
DS80000542D-page 4
2012-2017 Microchip Technology Inc.
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.
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© 2012-2017, Microchip Technology Incorporated, All Rights
Reserved.
ISBN: 978-1-5224-1795-8
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2012-2017 Microchip Technology Inc.
DS80000542D-page 5
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