AMD SC2200 User Manual
AMD Geode™ SC2200 Processor Data Book
117
SuperI/O Module
32580B
5.5.3
RTC Registers
The RTC registers can be accessed (see Section 5.4.2.1
"LDN 00h - Real-Time Clock" on page 104) at any time dur-
ing normal operation mode (i.e.,when V
"LDN 00h - Real-Time Clock" on page 104) at any time dur-
ing normal operation mode (i.e.,when V
SB
is within the rec-
ommended operation range). This access is disabled
during battery-backed operation. The write operation to
during battery-backed operation. The write operation to
these registers is also disabled if bit 7 of the CRD Register
is 0.
is 0.
Note:
Before attempting to perform any start-up proce-
dures, read about bit 7 (VRT) of the CRD Register.
dures, read about bit 7 (VRT) of the CRD Register.
This section describes the RTC Timing and Control Regis-
ters that control basic RTC functionality.
ters that control basic RTC functionality.
Table 5-19. RTC Register Map
Index
Type
Name
Reset
Type
00h
R/W
SEC. Seconds Register
V
PP
PUR
01h
R/W
SECA. Seconds Alarm Register
V
PP
PUR
02h
R/W
MIN. Minutes Register
V
PP
PUR
03h
R/W
MINA. Minutes Alarm Register
V
PP
PUR
04h
R/W
HOR. Hours Register
V
PP
PUR
05h
R/W
HORA. Hours Alarm Register
V
PP
PUR
06h
R/W
DOW. Day Of Week Register
V
PP
PUR
07h
R/W
DOM. Date Of Month Register
V
PP
PUR
08h
R/W
MON. Month Register
V
PP
PUR
09h
R/W
YER. Year Register
V
PP
PUR
0Ah
R/W
CRA. RTC Control Register A
Bit specific
0Bh
R/W
CRB. RTC Control Register B
Bit specific
0Ch
RO
CRC. RTC Control Register C
Bit specific
0Dh
RO
CRD. RTC Control Register D
V
PP
PUR
Programmable
1
R/W
DOMA. Date of Month Alarm Register
V
PP
PUR
Programmable
1
R/W
MONA. Month Alarm Register
V
PP
PUR
Programmable
1
R/W
CEN. Century Register
V
PP
PUR
1.
Overlaid on RAM bytes in range 0Eh-7Fh. See Section 5.4.2.1 "LDN 00h - Real-Time Clock" on page 104.
Table 5-20. RTC Registers
Bit
Description
Index 00h
Seconds Register - SEC (R/W)
Reset Type: V
PP
PUR
7:0
Seconds Data. Values may be 00 to 59 in BCD format or 00 to 3B in binary format.
Index 01h
Seconds Alarm Register - SECA (R/W)
Reset Type: V
PP
PUR
7:0
Seconds Alarm Data. Values may be 00 to 59 in BCD format or 00 to 3B in binary format.
When bits 7 and 6 are both set to one (“11”), unconditional match is selected.
Index 02h
Minutes Register - MIN (R/W)
Reset Type: V
PP
PUR
7:0
Minutes Data. Values can be 00 to 59 in BCD format, or 00 to 3B in binary format.
Index 03h
Minutes Alarm Register - MINA (R/W)
Reset Type: V
PP
PUR
7:0
Minutes Alarm Data. Values can be 00 to 59 in BCD format, or 00 to 3B in binary format.
When bits 7 and 6 are both set to 1, unconditional match is selected. See Section 5.5.2.5 "Alarms" on page 113 for more
information about “unconditional” matches.
information about “unconditional” matches.