MCP79411 datasheet(17/60 Pages) MICROCHIP

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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

110

Unimplemented

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.

ALARM X SECONDS (0X0A/0X11)

U-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

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