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CHAPTER 17
µ
PD178F054
User’s Manual U15104EJ2V0UD
17.1 Memory Size Switching Register (IMS)
The internal memory capacity of the
µ
PD178F054 can be changed using the memory size switching register (IMS).
By using this register, the memory of the
µ
PD178F054 can be mapped in the same manner as a mask ROM version
with a different internal memory capacity.
IMS is set with an 8-bit memory manipulation instruction.
Reset input sets this register to CFH.
Be sure to set IMS to C6H or C8H.
Figure 17-1. Format of Memory Size Switching Register (IMS)
RAM2
RAM1
RAM0
Selection of internal high-speed RAM capacity
0
1
0
512 bytes
1
1
0
1024 bytes
Other than above
Setting prohibited
ROM3 ROM2 ROM1 ROM0
Selection of internal ROM capacity
0
1
1
0
24 KB
1
0
0
0
32 KB
Other than above
Setting prohibited
Table 17-2 shows the setting of IMS to perform the same memory mapping as that of a mask ROM version.
Table 17-2. Set Value of Memory Size Switching Register
Targeted Model
Set Value of IMS
µ
PD178053
C6H
µ
PD178054
C8H
7
RAM2
6
RAM1
5
RAM0
4
0
3
ROM3
2
ROM2
1
ROM1
0
ROM0
Symbol
IMS
After reset
CFH
R/W
R/W
Address
FFF0H
Содержание mPD178053
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