Datasheet
2010-2013 Microchip Technology Inc. DS20002266E-page 17
MCP79410/MCP79411/MCP79412
7.0 ALARM REGISTERS
The MCP7941X family feature two independent
alarms. The registers associated with the alarms are
located at 0Ah-16h in the RTCC memory map.
The alarms feature independent interrupt flags and
interrupt polarity. The alarms interrupt is generated on
the MFP pin.
The alarm function on the MCP7941XX allows the user
to load a time into a series of registers that represent a
future time. When the current time reaches that set
time, the alarm is activated and an interrupt can be
generated. Using the alarm feature will allow the
system to offload the task to checking for a specific time
to the RTCC.
The alarms on the MCP7941X are not single-shot
trigger, that is, the alarm will retrigger immediately if the
current alarm still matches the set conditions. Clearing
the ALMxIF bit while the alarm match is still TRUE will
retrigger the alarm. The alarms offer programmable
match conditions:
For example, if the alarm is configured to match on the
minutes, when the match is TRUE the alarm will
retrigger until the match is FALSE. This would be
similar to trying to exit an interrupt on an MCU without
clearing the interrupt flag. It is suggested that the
Seconds, Minutes, Hour, Day, Date and Month match
condition.
Both Alarm0 and Alarm1 offer identical operation.
TABLE 7-1:
ALMxC<2:0> Match Condition Time Alarm match TRUE Duration
000 Seconds Only 1 Second
001 Minutes Only 1 Minute
010 Hours Only 1 Hour
011 Day Only 1 Day
100 Date Only 1 Day
101 Unimplemented NA
110 Unimplemented NA
111 Seconds, Minutes, Hour, Day, Date and Month 1 Second
Note: The X variable used in this section is used
to designate Alarm 0 or Alarm 1.
REGISTER 7-1: ALARM X SECONDS (0X0A/0X11)
U-0 R/W-0 R/W-0
— 10 Seconds Seconds
bit 7 bit 6 bit 4 bit 3 bit 0
Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set “0” = Bit is clear “X” = Bit is unknown
bit 7 Unimplemented: Read as ‘0’
bit 6-4 10 SECONDS<2:0>: Binary-Coded Decimal Value of Second’s Tens Digit
Contains a value from 0 to 5
bit 3-0 SECONDS<3:0>: Binary-Coded Decimal Value of Second’s Ones Digit
Contains a value from 0 to 9