MCP79411 datasheet(10/38 Pages) MICROCHIP

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MCP7941X

DS22266B-page 10

Preliminary

 2011 Microchip Technology Inc.

4.0

RTCC FUNCTIONALITY

The MCP7941x family is a highly integrated RTCC. On-

board time and date counters are driven from a low-

power oscillator to maintain the time and date. An

integrated VCC switch enables the device to maintain

the time and date and also the contents of the SRAM

during a VCC power failure.

4.1

RTCC MEMORY MAP

The RTCC registers are contained in addresses

0x00h-0x1fh. 64 bytes of user-accessable SRAM are

located in the address range 0x20-0x5f. The SRAM

memory is a separate block from the RTCC control

and Configuration registers. All SRAM locations are

battery-backed-up during a VCC power fail. Unused

locations are not accessible, MCP7941X will noACK

after the address byte if the address is out of range.

The shaded areas are not implemented and read as

‘0’. No error checking is provided when loading time

and date registers.

• Addresses 0x00h-0x06h are the RTCC Time and

Date registers. These are read/write registers.

Care must be taken when writing to these regis-

ters with the oscillator running.

• Incorrect data can appear in the Time and Date

registers if a write is attempted during the time

frame where these internal registers are being

incremented. The user can minimize the likeli-

hood of data corruption by ensuring that any

writes to the Time and Date registers occur before

the contents of the second register reach a value

of 0x59H.

• Addresses 0x07h-0x09h are the device Configu-

ration, Calibration and ID Unlock registers.

• Addresses 0x0Ah-0x10h are the Alarm 0 regis-

ters. These are used to set up the Alarm 0, the

Interrupt polarity and the Alarm 0 Compare.

• Addresses 0x11h-0x17h are the same as 0x0Bh-

0x11h but are used for Alarm 1.

• Addresses 0x18h-0x1Fh are used for the time-

stamp feature.

The Memory Map is shown in Table 4-1.

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