EP80579 Datasheet, PDF (1106/1916 Pages) Intel Corporation – Intel® EP80579 Integrated Processor Product Line

Intel^® EP80579 Integrated Processor
Table 29-1. I/O Registers
I/O Locations
70h and 74h
71h and 75h
72h and 76h
73h and 77h
If U128E bit = 0
Also alias to 72h and 76h
Also alias to 73h and 77h
Function:
Real-Time Clock (Standard RAM) Index Register
Note: Writes to 72h, 74h, and 76h do not affect NMI
enable (bit 7 of 70h)
Real-Time Clock (Standard RAM) Target Register
Extended RAM Index Register (if enabled)
Extended RAM Target Register (if enabled)
I/O locations 70h and 71h are the standard legacy location for the real-time clock. The
map for this bank is shown in Table 29-2. Locations 72h and 73h are for accessing the
extended RAM. The extended RAM bank is also accessed using an indexed scheme. I/O
address 72h is used as the address pointer and I/O address 73h is used as the data
register. Index addresses above 127h are not valid. If the extended RAM is not needed,
it may be disabled.
Note:
Software must preserve the value of bit 7 at I/O addresses 70h. When writing to this
address, software must first read the value, and then write the same value for bit 7
during the sequential address write. Note that port 70h is not directly readable. The
only way to read this register is through Alt Access mode. Although RTC Index bits
06:00 are readable from port 74h, bit 7 will always return 0. If the NMI# enable is not
changed during normal operation, software can alternatively read this bit once and
then retain the value for all subsequent writes to port 70h.
29.3
Real Time Clock Indexed Register Details
The RTC contains two sets of indexed registers that are accessed using the two
separate Index and Target registers (70/71h or 72/73h), as shown in Table 29-2.
Table 29-2. RTC (Standard) RAM Bank
Index
Name
00h
01h
02h
03h
04h
05h
06h
07h
08h
09h
0Ah
0Bh
0Ch
0Dh
0Eh – 7Fh
Seconds
Seconds Alarm
Minutes
Minutes Alarm
Hours
Hours Alarm
Day of Week
Day of Month
Month
Year
Register A
Register B
Register C
Register D
114 Bytes of User RAM
Intel^® EP80579 Integrated Processor Product Line Datasheet
1106
August 2009
Order Number: 320066-003US