
Memory Management
2-13
Table 2-7
MMS Mapping Example Settings
Instruction
Ports
Data
Comment
IOW
IOW
022h
023h
66h
xxx1 011x
Set on-board memory size to 8 Mbyte. Note that bits 7–5 are read
only because they affect the choice of bus.
IOW
IOW
022h
023h
74h
xxxx xx1x
Select MMSA for programming.
IOW
IOW
022h
023h
6Dh
0100 0000
Set MMSA base address to D0000h and I/O base address to
0208h.
IOW
IOW
022h
023h
6Ch
1000 0000
Set all translated MMSA A23s (page 7 = 1, others = 0).
IOW
IOW
022h
023h
6Eh
0000 1110
Set A22 and A21 for MMSA pages 0–3.
IOW
IOW
022h
023h
67h
1101 0000
Set A22 and A21 for MMSA pages 4–7.
IOW
IOW
IOW
IOW
IOW
IOW
IOW
IOW
0208h
2208h
4208h
6208h
8208h
A208h
C208h
E208h
1111 1111
1000 0000
0xxx xxxx
0xxx xxxx
0xxx xxxx
0xxx xxxx
1000 1000
1111 1111
Translate A20–A14 of MMSA page 0; enable the page.
Translate A20–A14 of MMSA page 1; enable the page.
Disable translation for MMSA page 2.
Disable translation for MMSA page 3.
Disable translation for MMSA page 4.
Disable translation for MMSA page 5.
Translate A20–A14 of MMSA page 6; enable the page.
Translate A20–A14 of MMSA page 7; enable the page.
IOW
IOW
022h
023h
71h
xxxx 0101
Set memory type for MMSA pages: 0–1 on board
(pages 2-3 not mapped).
IOW
IOW
022h
023h
72h
0000 xxxx
Set memory type for MMSA pages: 6–7 ROM DOS
(pages 4-5 not mapped).
IOW
IOW
022h
023h
65h
x1xx xxxx
Enable MMSA.
IOW
IOW
022h
023h
74h
xxxx xx01
Enable MMSB and select MMSB for programming.
IOW
IOW
022h
023h
6Ch
xxxx 0xxx
Set all translated MMSB A23s (pages 0,1, 2 not translated).
IOW
IOW
022h
023h
6Eh
10xx xxxx
Set A22 and A21 for MMSB page 3 (pages 0,1, 2 not translated).
IOW
IOW
IOW
IOW
0208h
2208h
4208h
6208h
0xxx xxxx
0xxx xxxx
0xxx xxxx
1000 0000
Disable translation for MMSB page 0.
Disable translation for MMSB page 1.
Disable translation for MMSB page 2.
Translate A20–A14 of MMSB page 3; enable the page.
IOW
IOW
022h
023h
73h
11xx xxxx
Set memory type for MMSB pages: 0–2 (unmapped), 3 (ROM
BIOS).