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CHAPTER 23 EXTERNAL DEVICE EXPANSION FUNCTION
1
1
48 Kbytes
56 Kbytes
Note 2
1
1
0
1
0
0
7
RAM2
Symbol
IMS
6
RAM1
5
RAM0
4
0
3
ROM3
2
ROM2
1
ROM1
0
ROM0
Address
FFF0H Note 1
After
Reset
R/W
R/W
Internal ROM size selectionROM3
60 Kbytes1
ROM2
1
ROM1
1
ROM0
0
Setting prohibitedOther than above
Internal high-speed RAM size selection
RAM2 RAM1 RAM0
1024 bytes110
Setting prohibitedOther than above
(2) Internal memory size switching register (IMS)
The
µ
PD78P078, 78P078Y can specify the internal memory size by internal memory size switching register
(IMS).
IMS is set with an 8-bit memory manipulation instruction.
RESET input sets this register to the value indicated in Table 23-5.
Figure 23-3. Internal Memory Size Switching Register Format
Notes 1. The values after reset depend on the product. (See Table 23-5)
Table 23-5. Values when the Internal Memory Size Switching Register is Reset
Type Number Reset Value
µ
PD78076, 78076Y CCH
µ
PD78078, 78078Y CFH
µ
PD78P078, 78P078Y
2. When using the external device expansion function in the
µ
PD78078, 78078Y, 78P078, and
78P078Y set the internal ROM size to 56 Kbytes.
Caution When using the mask ROM products, do not set the values other than CCH and CFH to the
IMS except for the cases where the external device extension function is used in
µ
PD78078
and 78078Y.
Remark IMS should be set according to the internal ROM capacity.