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CHAPTER 19
μ
PD78P0208
374
User’s Manual U11302EJ4V0UM
19.2 Internal Expansion RAM Size Switching Register
By setting the internal expansion RAM size swtiching register (IXS), the
μ
PD78P0208 can have the same
memory map as used in mask ROM versions that have a different internal expansion RAM capacity.
For the mask ROM versions, IXS does not need to be set.
IXS is set with an 8-bit memory manipulation instruction.
RESET input sets IXS to 0AH.
Cautions 1.
The internal expansion RAM size switching register (IXS) is only incorporated in the
μ
PD780206,
μ
PD780208, and
μ
PD78P0208.
When using a mask ROM version
μ
PD780204,
μ
PD780204A,
μ
PD780205,
μ
PD780205A,
μ
PD780206,
μ
PD780208, do not set a value other than those listed in Table 19-3 to IXS.
2.
Figure 19-2. Format of Internal Expansion RAM Size Switching Register
Table 19-3 lists the IXS setting values for a memory map equivalent to the mask ROM versions.
Table 19-3. Internal Expansion RAM Size Switching Register Setting Values
Target Mask ROM Version
IXS Setting Value
μ
PD780204, 780204A
μ
PD780205, 780205A
0CH
μ
PD780206
μ
PD780208
0AH
IXS is not incorporated in the
μ
PD780204,
μ
PD780204A,
μ
PD780205, and
μ
PD780205A.
However, if a write instruction to IXS is executed in the
μ
PD780204,
μ
PD780204A,
μ
PD780205, or
μ
PD780205A, the operation is not affected.
IX
RAM0
IXS
7
6
5
4
3
2
Symbol
1
0
IX
RAM3
Internal expansion RAM
capacity selection
FFF4H
IX
RAM1
IX
RAM3
IX
RAM2
0
0
0
0
Address
After reset
R/W
0AH
W
1
1024 bytes
1
No internal expansion RAM (0 bytes)
Setting prohibited
IX
RAM2
0
1
Other than above
IX
RAM1
1
0
IX
RAM0
0
0