FM33256/FM3316 SPI Companion w/ FRAM
Register Map
The RTC and processor companion functions are accessed via 30 special function registers, which are mapped to
unique op-codes. The interface protocol is described on page 17. The registers contain timekeeping data, alarm
settings, control bits, and information flags. A description of each register follows the summary table.
Register Map Summary Table
Battery-backed =
Nonvolatile =
BB/NV User Programmable =
Address
1Dh
1Ch
1Bh
1Ah
19h
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
D6
0
D5
D4
D3
D2
D1
D0
Function
Range
01-12
01-31
00-23
00-59
00-59
Alarm months
Alarm date
/Match
/Match
/Match
/Match
/Match
SNL
0
10 mo
Alarm Month
Alarm Date
10 date
Alarm 10 hours
Alarm 10 minutes
Alarm 10 seconds
0
Alarm hours
0
Alarm Hours
Alarm Minutes
Alarm Seconds
Companion Control
Serial Number 7
Serial Number 6
Serial Number 5
Serial Number 4
Serial Number 3
Serial Number 2
Serial Number 1
Serial Number 0
Event Counter 1
Event Counter 0
Event Counter Control
Watchdog Control
Watchdog Control
Watchdog Restart
Watchdog Flags
Years
Alarm minutes
Alarm seconds
AL/SW
F1
F0
VBC
FC
VTP1
VTP0
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
Event Counter Byte 1
Event Counter Byte 0
FFh
FFh
FFh
FFh
FFh
FFh
FFh
FFh
FFh
FFh
NVC
-
-
-
RC
WC
WDET2
WDST2
WR2
-
POLL
WDET1
WDST1
WR1
CP
WDET0
WDST0
WR0
-
WDE
-
-
WDSET4 WDET3
-
-
-
-
-
WDST4
WDST3
WR3
-
-
-
EWDF
LWDF
POR
LB
-
10 years
years
00-99
01-12
01-31
01-07
00-23
00-59
00-59
months
date
0
0
0
0
0
0
0
10 mo
Month
10 date
0
Date
day
0
0
0
Day
10 hours
hours
0
Hours
10 minutes
10 seconds
CALS
minutes
seconds
0
Minutes
0
Seconds
-
-
CAL4
AEN
CAL3
CAL2
CAL
CAL1
W
CAL0
R
CAL/Control
/OSCEN
AF
CF
reserved
RTC/Alarm Control
Note: When the device is first powered up and programmed, all timekeeping 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 and some of
the battery-backed bits. All other register values should be treated as unknown
.
Default Register Values
Address
1Dh
Hex Value
0x81
Address
12h
Hex Value
0x00
1Ch
1Bh
1Ah
19h
18h
17h
16h
15h
0x81
0x80
0x80
0x80
0x40
0x00
0x00
0x00
11h
10h
0Fh
0Eh
0Dh
0Ch
0Bh
01h
00h
0x00
0x00
0x00
0x00
0x01
0x00
0x00
0x00
14h
0x00
0x80
13h
0x00
Rev. 1.0
Dec. 2006
Page 12 of 28
RAMTRON [ RAMTRON INTERNATIONAL CORPORATION ]
