Zilog Z80180 - Manual (Page 73)

Z8018x
Family MPU User Manual
58
UM005003-0703
•
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.
Figure 27. Logical Memory Organization
Common
Bank Area
Common
Common
Bank Area
Common
Common
Common
Common Area 1
Lower Limit Address
>
Bank Area
Lower Limit Address
>
0000H
Common Area 1
Lower lImit Address
>
Bank Area
Lower lImit Address
=
0000H
Common Area 1
Lower Limit Address
=
Bank Area
Lower Limit Address
>
0000H
Common Area 1
Lower Limit Address
=
Bank Area
Lower Limit Address
=
0000H
(RESET Condition)
Area 1
Area 1
Area 0
Area 1 Area 1
Area 0