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22.2 ROM Mirror Function Selection Register (ROMM)
This section describes the configuration and functions of the ROM mirror function
selection register (ROMM).
■
ROMM (ROM mirror function selection register)
The diagram below shows the bit configuration of the ROM mirror function selection register
(ROMM).
bit
ROMM address: 00006F
(+): MB90F489B : Read only, fix to "1"
Other
: Selectable, initial value "0"
[bit9] MS
This bit selects the ROM mirror area.
•
"1": The ROM mirror area is 32 K bytes (008000
•
"0": The ROM mirror area is 48 K bytes (004000
Note:
In the MB90F489B, this bit is fixed to "1", and reading only can be used. Other device can be
selected.
[bit8] MI
This bit sets whether to enable or disable the ROM mirror function.
•
"1": Enable the mirror function.
•
"0": Disable the mirror function.
Notes:
• Do not access this register during accesses to address 004000
00FFFF
H
• If the ROM mirror function is started, addresses FF4000
are mirrored at addresses 004000
addresses of FF3FFF
function is enabled.
The value in ( ) is used if the MS bit is set to "1".
CHAPTER 22 ROM MIRROR FUNCTION SELECTION MODULE
15
14
13
-
-
-
H
).
(FF7FFF
H
H
12
11
10
9
-
-
-
MS
R/W
(+)
to 00FFFF
H
to 00FFFF
H
H
to 00FFFF
(008000
H
H
) or below are not mirrored in Bank 00 even if the ROM mirror
8
Initial value
MI
- - - - - - (+)1
B
R/W
).
H
).
H
to 00FFFF
(008000
H
H
to FFFFFF
(FF8000
to FFFFFF
H
H
to 00FFFF
) in Bank 00. ROM
H
H
to
H
)
H
475
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