Real Time Clock (Rtc) - AMD SB600 Technical Reference Manual

4.4

Real Time Clock (RTC)

Note: Some RTC functions are controlled by, and associated with, certain PCI configuration registers in the
SMBus/ACPI device. For more information refer to
0). The diagram below lists these RTC functions and the associated registers.
Function
For software compatibility, the RTC registers and RAM are accessed through two banks addressing – Bank
0 and Bank 1, which are shown in the diagram below. Bank 0 is selected if DV0 = 0(DV0 is the 5
Register A) while Bank 1 is chosen if DV0 = 1. Even if two banks are defined, the first 64 bytes (00H – 3FH)
of each bank share the same physical space. The SB600 has alternate RAM ports at h72/h73 as the
address/data ports. These two ports do not use the bank0/bank1 scheme. Memory can be accessed
directly using the 8-bit address port. Use of the two IO ports h72/h73 to access the RTC RAM is
highly recommended.
Note: Some RTC RAM space can be protected from read/write if corresponding bits are set to 1 in
RTCProtect register (PCI_Reg 6Ah).
©2008 Advanced Micro Devices, Inc.
AMD SB600 Register Reference Manual
section 2.3: SMBus Module and ACPI Block (Device 20,
RTC
RTC Ram Protection
External RTC Enable
RTC I/O Addr Enable
PCI_Reg:
64h
6Ah 78h
Proprietary
th
bit of
Real Time Clock (RTC)
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