MCP7940N-ESLASHMS datasheet(11/58 Pages) MICROCHIP

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DS20005010J-page 11

MCP7940N

5.0

FUNCTIONAL DESCRIPTION

The MCP7940N is a highly-integrated Real-Time

Clock/Calendar

(RTCC).

Using

on-board,

low-power oscillator, the current time is maintained in

seconds, minutes, hours, day of week, date, month,

and year. The MCP7940N also features 64 bytes of

general purpose SRAM. Two alarm modules allow

interrupts to be generated at specific times with flexible

comparison options. Digital trimming can be used to

compensate for inaccuracies inherent with crystals.

Using the backup supply input and an integrated power

switch, the MCP7940N will automatically switch to

backup power when primary power is unavailable,

allowing the current time and the SRAM contents to be

maintained. The time-stamp module captures the time

when primary power is lost and when it is restored.

The RTCC configuration and Status registers are used

to access all of the modules featured on the

MCP7940N.

5.1

Memory Organization

The MCP7940N features two different blocks of mem-

ory: the RTCC registers and general purpose SRAM

(Figure 5-1). They share the same address space,

accessed through the ‘1101111X’ control byte.

Unused locations are not accessible. The MCP7940N

will not acknowledge if the address is out of range, as

shown in the shaded region of the memory map in

Figure 5-1.

The RTCC registers are contained in addresses

0x00-0x1F. Table 5-1 shows the detailed RTCC regis-

ter map. There are 64 bytes of user-accessible SRAM,

located in the address range 0x20-0x5F. The SRAM is

a separate block from the RTCC registers. All RTCC

registers and SRAM locations are maintained while

operating from backup power.

FIGURE 5-1:

MEMORY MAP

Time and Date

SRAM (64 Bytes)

Power-Fail/Power-Up Time-Stamps

Alarm 1

Alarm 0

Configuration and Trimming

0x00

0x06

0x07

0x09

0x0A

0x10

0x11

0x17

0x18

0x1F

0x20

0x5F

0x60

0xFF

Unimplemented; device does not ACK

I2C Address:

1101111x

RTCC Registers/SRAM

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