W83977G Winbond Electronics Corp America, W83977G Datasheet - Page 104

• Manufacturer Part Number: W83977G
• Description: W83877TF plus KBC, CIR, RTC, Pb-free
• Manufacturer: Winbond Electronics Corp America

9. REAL-TIME CLOCK (RTC) AND "ON-NOW" CONTROL
The RTC with 242 bytes of RAM is a low-power device that provides a time-of-day clock in various
formats, and a calendar with century register. It has two alarms and three programmable interrupts. It
is also equipped with external battery backup capability for keeping time and saving RAM data under
power-failure situation.
The RTC software is compatible with the MC146818 Clock chip.
The "On-Now" Control enables PC to be powered on by several trigger events, a telephone ring for
example. Also, it allows a safely controlled power-off procedure executed in an orderly fashion.
9.1
Table 9.1.1, table 9.1.2, and table 9.1.3 show the register map of RTC and "On-Now" . These
registers are separated into three banks: Bank 0, Bank 1, and Bank 2. Bank 0 contains 10 bytes of
time, calendar, and alarm A data, four bytes of control/status registers, and 114 bytes of general
purpose user RAM.
TABLE 9.1.1 - REAL TIME CLOCK ADDRESS MAP BANK 0
In Bank 1, there are 128 bytes of general purpose user RAM, as shown in table 9.1.2.
ADDRESS
0Eh-7Fh
W83977F-A/ W83977G-A/ W83977AF-A/ W83977AG-A
0Ah
0Bh
0Ch
0Dh
00h
01h
02h
03h
04h
05h
06h
07h
08h
09h
REGISTER ADDRESS MAP
REGISTER TYPE
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R
R
-96
Register 00h : Seconds
Register 01h : Seconds Alarm A
Register 02h : Minutes
Register 03h : Minutes Alarm A
Register 04h : Hours
Register 05h : Hours Alarm A
Register 06h : Day of Week
Register 07h : Date of Month
Register 08h: Month
Register 09h : Year
Register 0Ah : Control Register
Register 0Bh : Control Register (Bit 0 is Read only)
Register 0Ch : Status Register
Register 0Dh : Status Register
Register 0Eh-7Fh : User RAM
REGISTER FUNCTION