Sharp MZ-80A Owner's Manual page 154

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164
3.1.1
Memory configurations
The memory
map for the MZ-80A
is
shown
in
Figure 3.2. The screened
parts
of
the figure indicate
user
area,
and
the 32 K bytes of main memory RAM are the standard package. The
remaining
16 K
bytes of
main
memory RAM
area
optional, and
can
be installed in the RAM socket provided
on
the
CPU
board.
The 4
K bytes of main memory area which are indicated
by the
dark
screening
can be used for swapping the address
spaces used
by
the MONITOR ROM. The left side of the figure shows the memory map under normal
conditions,
while
the right side shows the memory map when the MONITOR ROM has been swapped. As is shown
in
Table
3.1
,
memory
swaps
are
performed under control of memory mapped
I/O
by executing memory read instructions
such as
the follow¬
ing.
To place the memory in the state shown
on
the right
LD
A, (EOOCH)
To
place
the memory in the
state
shown on the left
LD
A, (E010H)
The memory configuration shown
on
the right is especailly
effective
when the
system
programs used start
at
address
$0000
and when the system programs utilized make active
use of
interrupt
processing.
$0000
$1000
$9000
SDOOO
SE000
SFOOO
SFFFF
MONITOR
ROM
4
K
bytes
Main memory
RAM
32 K
bytes
(standard package)
RAM
16 K
bytes
(expansion area)
Video RAM
area
Memory mapped
I/O
area
Floppy drive
control area
S0000
$1000
$9000
SBFFF
$C000K
=D
SDOOO
SE000
SFOOO
SFFFF
Main memory
RAM
(MONITOR)
ROM
4
K
bytes
Video RAM
area
Memory
mapped
I/O
area
Floppy drive
control
area
Figure
3.2
Memory maps
for normal
state and memory
swap state.

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