FM33256B
Document Number: 001-86213 Rev. *C
Page 20 of 39
POR
Power-On Reset: When the RST signal is activated by V
DD
< V
TP
, the POR bit will be set to ‘1’. A manual reset will
not set this flag. Note that one or both of the watchdog flags and the POR flag could be set if both reset sources
have occurred since the flags were cleared by the user. Battery-backed, read/write. (internally set, user must clear
bit).
LB
Low Backup: If the V
BAK
source drops to a voltage level insufficient to operate the RTC/alarm when V
DD
< V
BAK
,
this bit will be set to ‘1’. All registers need to be re-initialized since the battery-backed register values should be
treated as unknown. The user should clear it to ‘0’ when initializing the system. Battery-backed. Read/Write
(internally set, user must clear bit).
08h
Timekeeping – Years
D7
D6
D5
D4
D3
D2
D1
D0
10 year.3
10 year.2
10 year.1
10 year.0
Year.3
Year.2
Year.1
Year.0
Contains the lower two BCD digits of the year. Lower nibble contains the value for years; upper nibble contains the
value for 10s of years. Each nibble operates from 0 to 9. The range for the register is 0-99. Battery-backed,
read/write.
07h
Timekeeping – Months
D7
D6
D5
D4
D3
D2
D1
D0
0
0
0
10 Month
Month.3
Month.2
Month.1
Month.0
Contains the BCD digits for the month. Lower nibble contains the lower digit and operates from 0 to 9; upper nibble
(one bit) contains the upper digit and operates from 0 to 1. The range for the register is 1-12. Battery-backed,
read/write.
06h
Timekeeping – Date of the month
D7
D6
D5
D4
D3
D2
D1
D0
0
0
10 date.1
10 date.0
Date.3
Date.2
Date.1
Date.0
Contains the BCD digits for the date of the month. Lower nibble contains the lower digit and operates from 0 to 9;
upper nibble contains the upper digit and operates from 0 to 3. The range for the register is 1-31. Battery-backed,
read/write.
05h
Timekeeping – Day of the week
D7
D6
D5
D4
D3
D2
D1
D0
0
0
0
0
0
Day.2
Day.1
Day.0
Lower nibble contains a value that correlates to day of the week. Day of the week is a ring counter that counts from
1 to 7 then returns to 1. The user must assign meaning to the day value, as the day is not integrated with the date.
Battery-backed, read/write.
04h
Timekeeping – Hours
D7
D6
D5
D4
D3
D2
D1
D0
0
0
10 hours.1
10 hours.0
Hours.3
Hours.2
Hours.1
Hours.0
Contains the BCD value of hours in 24-hour format. Lower nibble contains the lower digit and operates from 0 to 9;
upper nibble (two bits) contains the upper digit and operates from 0 to 2. The range for the register is 0-23.
Battery-backed, read/write.
Table 7. Register Description
(continued)
Address
Description
