FM3104/16/64/256
Rev 0.2
May 2003
Page 12 of 22
09h
Watchdog Restart & Flags
D7
D6
D5
D4
D3
D2
D1
D0
WTR
Watchdog Timer Reset Flag: When the /RST signal is activated by the watchdog the WTR bit will be set to 1. It
must be cleared by the user. Note that both WTR and POR could be set if both reset sources have occurred since
the flags were cleared by the user. Battery-backed. Read/Write (internally set, user can only clear this bit).
Power-on Reset Flag: When the /RST signal is activated by VDD < VTP, the POR bit will be set to 1. It must be
cleared by the user. Note that both WTR and POR could be set if both reset sources have occurred since the flags
were cleared by the user. Battery-backed. Read/Write (internally set, user can only clear this bit).
Low Backup Flag: On power up, if the VBAK source is below the minimum voltage to operate the RTC and event
counters, this bit will be set to 1. The user should clear it to 0 when initializing the system. Battery-backed.
Read/Write (internally set, user can only clear this bit).
Watchdog Restart: Writing a pattern 1010b to WR3-0 restarts the watchdog timer. The upper nibble contents do
not affect this operation. Writing any pattern other than 1010b to WR3-0 has no effect on the timer. This allows
users to set or clear the WTR and POR flags without affecting the watchdog timer. Write-only.
Timekeeping – Years
D7
D6
D5
D4
POR
LB
-
WR3
WR2
WR1
WR0
WTR
POR
LB
WR3-0
08h
D3
D2
D1
D0
10 year.3
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.
Timekeeping – Months
D7
D6
D5
D4
10 year.2
10 year.1
10 year.0
Year.3
Year.2
Year.1
Year.0
07h
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.
Timekeeping – Date of the month
D7
D6
D5
D4
06h
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.
Timekeeping – Day of the week
D7
D6
D5
D4
05h
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.
Timekeeping – Hours
D7
D6
D5
D4
04h
D3
D2
D1
D0
0
0
10 hours.1
10 hours.0
Hours.3
Hours2
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.
Timekeeping – Minutes
D7
D6
D5
D4
03h
D3
D2
D1
D0
0
10 min.2
10 min.1
10 min.0
Min.3
Min.2
Min.1
Min.0
Contains the BCD value of minutes. Lower nibble contains the lower digit and operates from 0 to 9; upper nibble
contains the upper minutes digit and operates from 0 to 5. The range for the register is 0-59. Battery-backed,
read/write.
Timekeeping – Seconds
D7
D6
D5
D4
02h
D3
D2
D1
D0
0
10 sec.2
10 sec.1
10 sec.0
Seconds.3
Seconds.2
Seconds.1
Seconds.0
Contains the BCD value of seconds. Lower nibble contains the lower digit and operates from 0 to 9; upper nibble
contains the upper digit and operates from 0 to 5. The range for the register is 0-59. Battery-backed, read/write.