NEC 26.2 Internal Expansion RAM Size Switching Register

539
CHAPTER 26 µ PD78P058F, 78P058FY
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
26.2 Internal Expansion RAM Size Switching Register
The internal expansion RAM size of the µ PD78P058F and 78P058FY can be defined using the internal expansion
RAM size switching register (IXS), thus enabling memory mapping that is the same as that of mask ROM products
with different internal expansion RAM. The IXS is set by an 8-bit memory manipulation instruction.
RESET signal input sets IXS to 0AH.
Figure 26-2. 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 26-3.
Table 26-3. Value Set to the Internal Expansion RAM Size Switching Register
Pertinent Mask ROM Versions Value Set to IXS
µ PD78056F, 78056FY
µ PD78058F, 78058FY
Remark If a program for the
µ PD78P058F or 78P058FY which includes “MOV IXS, #0CH” is implemented with
the µ PD78056F, or 78056FY, this instruction is ignored and causes no malfunction.
0CH
0AH