82596DX Datasheet, PDF (25/77 Pages) Intel Corporation – HIGH-PERFORMANCE 32-BIT LOCAL AREA NETWORK COPROCESSOR

82596DX SX
The following diagram illustrates the format of the SCP
31
ODD WORD
16 15
EVEN WORD
0
XXXXXXXX
SYSBUS
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0FFFFF4h
X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X 0FFFFF8h
A31
A24 A23
ISCP ADDRESS
A0 0FFFFFCh
A31
A24 are not checked in 82586 mode
X
X areas are not checked in 82586 mode they must be 0 in all other modes
290219 – 14
ISCP ADDRESS The physical address of the ISCP In the 82586 mode bits A31 – A24 are considered to
be zero
Figure 15 The System Configuration Pointer
Writing the Sysbus
When writing the Sysbus byte it is important to pay attention to the byte order
 When a Little Endian processor is used the Sysbus byte is located at byte address 00FFFFF6h (or address
n ^a2 if an alternative SCP address n was programmed)
 When a processor using Big Endian byte ordering is used the SYSBUS alternative SCP and ISCP ad-
dresses will be different
 The Sysbus byte is located at 00FFFFF7h
 If an alternative SCP address is programmed the SYSBUS byte should be at byte address n ^a1
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