FM31T372 Datasheet, PDF (11/26 Pages) Ramtron International Corporation – System Supervisor & Temperature Compensated RTC(TCXO) with Embedded Crystal

FM31T372/374/376/378-G
Register Map
The TCXO and processor companion functions are accessed via 25 special function registers mapped to a separate
2-wire device ID. The interface protocol is described below. The registers contain timekeeping data, control bits, or
information flags. A description of each register follows the summary table below.
Register Map Summary Table
Nonvolatile =
Battery-backed =
Address
18h
17h
16h
15h
14h
13h
12h
11h
10h
0Fh
0Eh
0Dh
0Ch
0Bh
0Ah
09h
08h
07h
06h
05h
04h
03h
02h
01h
00h
D7
SNL
WDE
W TR
0
0
0
0
0
0
/OSCEN
reserved
Data
D6
D5
D4
D3
Serial Number Byte 7
Serial Number Byte 6
Serial Number Byte 5
Serial Number Byte 4
Serial Number Byte 3
Serial Number Byte 2
Serial Number Byte 1
Serial Number Byte 0
Counter 2 MSB
Counter 2 LSB
Counter 1 MSB
Counter 1 LSB
RC
FOEN
FC
WP1
WP0
-
-
WDT4 W DT3
POR
LB
-
WR3
10 years
0
0
10 mo
0
10 date
0
0
0
0
0
10 hours
10 minutes
10 seconds
CALS
CAL5
CAL4
CAL3
CF reserved reserved reserved
D2
D1
CC
C2P
VBC
VTP1
WDT2 WDT1
WR2
WR1
years
months
date
day
hours
minutes
s econds
CAL2
CAL1
CAL
W
D0
C1P
VTP0
WDT0
WR0
CAL0
R
Function
Range
Serial Number 7
FFh
Serial Number 6
FFh
Serial Number 5
FFh
Serial Number 4
FFh
Serial Number 3
FFh
Serial Number 2
FFh
Serial Number 1
FFh
Serial Number 0
FFh
Event Counter 2 MSB FFh
Event Counter 2 LSB FFh
Event Counter 1 MSB FFh
Event Counter 1 LSB FFh
Event Count Control
Companion Control
Watchdog Control
Watchdog Restart/Flags
Years
00-99
Month
1-12
Date
1-31
Day
1-7
Hours
0-23
Minutes
0-59
Seconds
0-59
OSC/CAL Control
RTC Control
Note: When the device is first powered up and programmed, all registers must be written because the
battery-backed register values cannot be guaranteed. The table below shows the default values of the non-volatile
registers. All other register values should be treated as unknown.
Default Register Values
Address Hex Value
18h
0x00
17h
0x00
16h
0x00
15h
0x00
14h
0x00
13h
0x00
12h
0x00
11h
0x00
0Bh
0x40
0Ah
0x1F
01h Factory
programmed
Rev. 1.1
Apr. 2011
Page 11 of 26