82C836 Datasheet, PDF (122/205 Pages) List of Unclassifed Manufacturers – Single-Chip 386sx AT

s Configuration Registers
82C386 CHIPSet Data Sheet
Table 10-13. Index 4EH----Extended Memory Boundary (continued)
Bit
Name
3-0
Extended
Boundary
Description
These bits specify the upper boundary of memory within the total memory
defined by internal configuration register 4DH. Memory residing above this
boundary is accessible only via EMS.
Bits
3210
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
Extended Memory Boundary
No limit (default); entire DRAM accessible
1MB (i.e., no extended memory)
1.25MB
1.5MB
2MB
3MB
4MB
5MB
7MB
8MB
9MB
10MB
11MB
12MB
13MB
15MB
Table 10-14. Index 4FH----EMS Control Register
Bit
Name
Description
7
EMS Address
This bit enables EMS memory access.
Translation Enable
0 = EMS is disabled (default).
1 = EMS is enabled .
6
EMS I/O Enable This bit enables access to the EMS I/O ports.
0 = EMS I/O port access is disabled (default).
1 = EMS I/O port access is enabled.
5-1
----
Reserved.
0
I/O Base
This bit specifies which I/O ports are used to read or write EMS page
registers.
0 = I/O ports 0208H, 0209H, and 020AH (default).
1 = I/O ports 0218H, 0219H, and 021AH.
1 0-1 0 Revision 3.0
PRELIMINARY
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