Internal Expansion Ram Size Switching Register; Value Set To The Internal Expansion Ram Size Switching Register - NEC PD78056F User Manual

26.2 Internal Expansion RAM Size Switching Register

The internal expansion RAM size of the 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
Symbol 7 6 5
IXS 0 0 0
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
Remark If a program for the PD78P058F or 78P058FY which includes "MOV IXS, #0CH" is implemented with
the PD78056F, or 78056FY, this instruction is ignored and causes no malfunction.
CHAPTER 26 PD78P058F, 78P058FY
4 3 2 1 0
0 IXRAM3 IXRAM2 IXRAM1 IXRAM0
Pertinent Mask ROM Versions
PD78056F, 78056FY
PD78058F, 78058FY
After
Address
Reset
FFF4H 0AH
IXRAM3 IXRAM2 IXRAM1 IXRAM0 Internal Extension RAM Capacity Selection
1 1 0 0 0 bytes
1 0 1 0 1024 bytes
Other than above Setting prohibited
Value Set to IXS
0CH
0AH
R/W
W
539