Datasheet

MCP7941X
DS22266A-page 10 Preliminary  2010 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 V
CC 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 V
CC 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 accessing these regis-
ters while the oscillator is running.
• 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.
TABLE 4-1: RTCC MEMORY MAP
Address Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Function Range
Reset
State
00h ST 10 Seconds Seconds Seconds 00-59 00h
01h
10 Minutes Minutes Minutes 00-59 00h
02h
12/24
10 Hour
AM/PM
10 Hour Hour Hours 1-12 + AM/PM
00 - 23
00h
03h
OSCON VBAT VBATEN Day Day 1-7 01h
04h
10 Date Date Date 01-31 01h
05h
LP 10 Month Month Month 01-12 01h
06h 10 Year Year Year 00-99 01h
07h OUT SQWE ALM1 ALM0 EXTOSC RS2 RS1 RS0 Control Reg. 80h
08h CALIBRATION Calibration 00h
09h UNIQUE UNLOCK ID SEQUENCE Unlock ID 00h
0Ah 10 Seconds Seconds Seconds 00-59 00h
0Bh
10 Minutes Minutes Minutes 00 - 59 00h
0Ch
12/24
10 Hour
AM/PM
10 Hours Hour Hours 1-12 + AM/PM
00-23
00h
0Dh ALM0POL ALM0C2 ALM0C1 ALM0C0 ALM0IF Day Day 1-7 01h
0Eh
10 Date Date Date 01-31 01h
0Fh
10 Month Month Month 01-12 01h
10h Reserved – Do not use Reserved 01h
11h 10 Seconds Seconds Seconds 00-59 00h
12h
10 Minutes Minutes Minutes 00-59 00h
13h
12/24
10 Hour
AM/PM
10 Hours Hour Hours 1-12 + AM/PM
00-23
00h
14h ALM1POL ALM1C2 ALM1C1 ALM1C0 ALM1IF Day Day 1-7 01h
15h
10 Date Date Date 01-31 01h
16h
10 Month Month Month 01-12 01h
17h Reserved - Do not use Reserved 01h
18h
10 Minutes Minutes 00h
19h
12/24
10 Hour
AM/PM
10 Hours Hour 00h
1Ah
10 Date Date 00h
1Bh Day 10 Month Month 00h
1Ch 10 Minutes Minutes 00h
1Dh
12/24
10 Hour
AM/PM
10 Hours Hour 00h
1Eh
10 Date Date 00h
1Fh Day 10 Month Month 00h