Datasheet

 2012-2018 Microchip Technology Inc. DS20002300C-page 11
MCP7951X/MCP7952X
5.0 FUNCTIONAL DESCRIPTION
The MCP795XX is a highly-integrated Real-Time
Clock/Calendar (RTCC). Using an on-board,
low-power oscillator, the current time is maintained in
hundredths of seconds, seconds, minutes, hours, day
of week, date, month, and year. The MCP795XX also
features 64 bytes of general purpose SRAM, either
2 Kbits (MCP7952X) or 1 Kbit (MCP7951X) of
EEPROM, and 16 bytes of protected EEPROM. 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 MCP795XX will
automatically switch to backup power when primary
power is unavailable, allowing the current time and the
SRAM contents to be maintained. The timestamp
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
MCP795XX.
5.1 Memory Organization
The MCP795XX features four different blocks of
memory: the RTCC registers, general purpose SRAM,
2 Kbit EEPROM (1 Kbit for the MCP7951X) with
software write-protect, and protected EEPROM. The
RTCC registers and SRAM share the same address
space and are accessed through the READ and WRITE
instructions. The EEPROM region is accessed using
the EEREAD and EEWRITE instructions, and the
protected EEPROM is accessed using the IDREAD and
IDWRITE instructions. Unused locations are not
accessible. The MCP795XX will not return valid data if
the address is out of range, as shown in the shaded
region of the memory maps in Figure 5-1 and
Figure 5-2.
The RTCC registers are contained in addresses
0x00-0x1F. Tabl e 5-1 shows the detailed RTCC
register 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 FOR MCP7951X
Time and Date
SRAM (64 Bytes)
Power-Fail/Power-Up Timestamps
Alarm 1
Alarm 0
Configuration and Trimming
0x00
0x07
0x08
0x0B
0x0C
0x11
0x12
0x17
0x18
0x1F
0x20
0x5F
0x60
0xFF
Unimplemented; device does not respond
RTCC Registers/SRAM
Protected EEPROM (16 Bytes)
0x00
0xFF
0x00
0x07
0x08
0x0F
Lockable User ID (16 Bytes)
EEPROM
EUI-48/EUI-64 Node Address
Unimplemented; mapped back to 0x00-0x7F
0x7F
0x80
EEPROM (128 Bytes)
Protected EEPROM