Z80180 Datasheet, PDF (73/326 Pages) Zilog, Inc. – Z8018x Family MPU

Z 8018x Fam ily
M PU Us e r M anual
58
• MMU Common/Bank Area Register (CBAR)
• MMU Common Base Register (CBR)
• MMU Bank Base Register (BBR)
CBAR is used to define the logical memory organization, while CBR and
BBR are used to relocate logical areas within the 1024KB physical
address space. The resolution for both setting boundaries within the
logical space and relocation within the physical space is 4KB.
The CA field of CBAR determines the start address of Common Area 1
(Upper Common) and by default, the end address of the Bank Area. The
BA field determines the start address of the Bank Area and by default, the
end address of Common Area 0 (Lower Common).
The CA and BA fields of CBAR may be freely programmed subject only
to the restriction that CA may never be less than BA. Figures 27 and 28
illustrate examples of logical memory organizations associated with
different values of CA and BA.
Common
Area 1
Bank Area
Common
Area 0
Common
Area 1
Bank Area
Common
Area 1
Common
Area 0
Common
Area 1
Common Area 1 Common Area 1 Common Area 1 Common Area 1
Lower Limit Address Lower lImit Address Lower Limit Address Lower Limit Address
>
>
=
=
Bank Area
Bank Area
Bank Area
Bank Area
Lower Limit Address Lower lImit Address Lower Limit Address Lower Limit Address
>
=
>
=
0000H
0000H
0000H
0000H
(RESET Condition)
Figure 27. Logical Memory Organization
UM005001-ZMP0400