PC87417 Datasheet, PDF (84/257 Pages) National Semiconductor (TI) – LPC ServerI/O for Servers and Workstations

3.0 Device Architecture and Configuration (Continued)
3.15.12 X-Bus Memory Configuration Register 2 (XMEMCNF2)
This register is reset by hardware to 00h.
Power Well:V_SB
Location:Index F8h
Type: Varies per bit
Bit
7
6
5
4
3
2
1
0
Name
LOCKMMP
Reserved
SEL2UDM SEL2BIOS
BIOSIZE
Reset
0
0
0
0
0
0
0
0
Bit
Description
7 LOCKMMP (Lock Memory Address Map). When set to 1, this bit locks the configuration of registers
XMEMCNF1, XMEMCNF2, XMEMBAH, XMEMBAL and XMEMSIZE by disabling writing to all their bits
(including to the LOCKMAP bit itself). Once set, this bit can be cleared either by V_DD Power-Up reset (or
Hardware reset) or by V_SB Power-Up reset, according to the VSBLOCK bit in the ACBLKCTL register (see
Section 6.3.4 on page 128). In addition, this bit is cleared by setting the UNLOCKX bit in the ACBLKCTL register
(PC87417).
0: R/W bits are enabled for write (default)
1: All bits are RO
6-5 Reserved.
4 SEL2UDM (Dual User-Defined Memory Select Enable). Enables the PC8741x device to control two memory
devices for data storage. The second zone (MEM Zone 1) is mapped on top of the first zone (MEM Zone 0).
Both zones are the same size. The base address of MEM Zone 0 is specified by the XMEMBAH and XMEMBAL
registers. The size of both memory zones is specified by the XMEMSIZE register. The base address of MEM
Zone 1 is: (Base Address Memory Zone) + (Size Memory Zone).
0: Disabled - Use only MEM Zone 0, if enabled (default)
1: Enabled - If the user-defined memory is enabled, use both MEM Zone 0 and MEM Zone 1
3 SEL2BIOS (Dual BIOS Select Enable). Enables the PC8741x device to control two flash devices for BIOS
storage. The first device (BIOS Zone 0) is used for legacy and the upper 386 zone. BIOS zone 1 is on the next
“BIOS Size” block in the 386 address range (addresses lower than these of Block 1). When FWH is enabled,
BIOS Zone 0 responds to the upper addresses and BIOS Zone 1, if enabled, responds to the group below Zone
0, as defined by BIOS Size. Both zones use the same FWHID value.
0: Disabled - Use BIOS Zone 0 only, if enabled (default)
1: Enabled - If either the LPC BIOS or the FWH BIOS is enabled, use both BIOS Zone 0 and BIOS Zone 1
2-0 BIOSIZE (BIOS Size). Define the Size of one BIOS Zone in the 386 range. Note that by setting the Dual BIOS
Select Enable, two equal-sized BIOS Zones are available.
Bits
2 1 0 Size (Bytes)
0 0 0:
0 0 1:
0 1 0:
0 1 1:
1 0 0:
1 0 1:
1 1 0:
1 1 1:
256 Kbytes (default)
512 Kbytes
1 Mbyte
2 Mbytes
4 Mbytes
8 Mbytes
16 Mbytes
Reserved
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