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CHAPTER 26
µ
PD78P054, 78P058
7
0
Symbol
IXS
6
0
5
0
4
0
3
IXRAM3
2
IXRAM2
1
IXRAM1
0
IXRAM0
Address
FFF4H 0AH
After
Reset
Internal extension RAM capacity selection
IXRAM3
IXRAM2IXRAM1
1024 bytes101
Setting prohibitedOther than above
IXRAM0
0
R/W
W
0 bytes1100
26.3 Internal Expansion RAM Size Switching Register
The
µ
PD78P058 allows users to define its internal expansion RAM size using the internal expansion RAM size
switching register (IXS), so that the same memory mapping as that of a mask ROM version with a different-size internal
expansion RAM is possible. The IXS is set by an 8-bit memory manipulation instruction.
RESET signal input sets IXS to 0AH.
Figure 26-3. Internal Expansion RAM Size Switching Register Format
The value in the IXS that has the identical memory map to the mask ROM versions is given in Table 26-5.
Table 26-5. Value Set to the Internal Expansion RAM Size Switching Register
Pertinent mask ROM versions Value set to IXS
µ
PD78052, 78052Y
µ
PD78053, 78053Y
µ
PD78054, 78054Y
µ
PD78055, 78055Y
µ
PD78056, 78056Y
µ
PD78058, 78058Y
Remark If a program for the
µ
PD78P058 or 78P058Y which
includes “MOV IXS, #0CH” is implemented with the
µ
PD78055, 78055Y, 78056, or 78056Y, this
instruction is ignored and causes no malfunction.
0CH
0AH