User's Manual

DIGITAL-LOGIC AG MSM855/HLV/B/B2 Detailed Manual V1.0A
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5.6.3. ROM-BIOS Sockets
An EPROM socket with 8bit wide data access normally contains the board's AT compatible ROM-BIOS. The
socket takes an E82802AC8 EPROM (or equivalent) device. The board's wait-state control logic
automatically inserts four memory wait-states in all CPU accesses to this socket. The ROM-BIOS sockets
occupy the memory area from C0000H through FFFFFh; however, the board's ASIC logic reserves the entire
area from C0000h through FFFFFh for onboard devices, so that this area is already usable for ROM-DOS
and BIOS expansion modules. Consult the appropriate address map for the MICROSPACE MSM855 ROM-
BIOS sockets.
5.7. CMOS RAM Map
Systems based on the industry-standard specification include a battery backed Real Time Clock chip. This
clock contains at least 64Bytes of non-volatile RAM. The system BIOS uses this area to store information
including system configuration and initialization parameters, system diagnostics, and the time and date. This
information remains intact even when the system is powered down.
The BIOS supports 128Bytes of CMOS RAM. This information is accessible through I/O ports 70h and 71h.
CMOS RAM can be divided into several segments:
 Locations 00h - 0Fh contain real time clock (RTC) and status information
 Locations 10h - 2Fh contain system configuration data
 Locations 30h - 3Fh contain System BIOS-specific configuration data as well as chipset-specific
information
 Locations 40h - 7Fh contain chipset-specific information as well as power management configuration
parameters
The following table provides a summary of how these areas may be further divided.
Beginning Ending Checksum Description
00h 0Fh No RTC and Checksum
10h 2Dh Yes System Configuration
2Eh 2Fh No Checksum Value of 10h - 2Dh
30h 33h No Standard CMOS
34h 3Fh No Standard CMOS - SystemSoft Reserved
40h 5Bh Yes Extended CMOS - Chipset Specific
5Ch 5Dh No Checksum Value of 40h - 5Bh
5Eh 6Eh No Extended CMOS - Chipset Specific
6Fh 7Dh Yes Extended CMOS - Power Management
7Eh 7Fh No Checksum Value of 6Fh - 7Dh