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AMD Geode™ SC3200 Processor Data Book 109
SuperI/O Module
32581C
5.5.3 RTC Registers
The RTC registers can be accessed (see Section 5.4.2.1
"LDN 00h - Real-Time Clock" on page 96) 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
these registers is also disabled if bit 7 of the CRD Register
is 0.
Note: Before attempting to perform any start-up proce-
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.
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 96.
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.