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CHAPTER 27
µ
PD78P078, 78P078Y
7
RAM2
Symbol
IMS
6
RAM1
5
RAM0
4
0
3
ROM3
2
ROM2
1
ROM1
0
ROM0
Address
FFF0H CFH
After
Reset
R/W
R/W
1
1
Internal ROM Capacity Selection
48 Kbytes
56 Kbytes
Note
ROM3
60 Kbytes1
1
1
ROM2
1
0
1
ROM1
1
0
0
ROM0
1
Setting prohibitedOther than above
Internal High-Speed RAM Capacity Selection
RAM2 RAM1 RAM0
1024 bytes110
Setting prohibitedOther than above
27.1 Internal Memory Size Switching Register
The
µ
PD78P078 and 78P078Y allow users to define its internal memory sizes using the internal memory size
switching register (IMS), so that the same memory mapping as that of a mask ROM version with a different-size
internal ROM is possible.
IMS is set with an 8-bit memory manipulation instruction.
RESET input sets IMS to CFH.
Figure 27-1. Internal Memory Size Switching Register Format
Note When using the external device extension function on the following devices, the internal ROM capacity
must be 56 Kbytes or less:
µ
PD78078, 78078Y, 78P078, 78P078Y.
Caution When using the mask ROM versions, do not set the values other than CCH and CFH to the IMS
except for the case where the external device extension function is used on the
µ
PD78078 and
78078Y.
The IMS settings to give the same memory map as mask ROM versions are shown in Table 27-2.
Table 27-2. Examples of Internal Memory Size Switching Register Settings
Relevant Mask ROM Version IMS Setting
µ
PD78076, 78076Y CCH
µ
PD78078, 78078Y CFH