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CHAPTER 22 EXTERNAL DEVICE EXPANSION FUNCTION
1
1
48 Kbytes
56 Kbytes
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
After
Reset
R/W
R/W
Internal ROM size selectionROM3
60 Kbytes1
ROM2
1
ROM1
1
ROM0
1
Setting prohibitedOther than above
Internal high-speed RAM size selection
RAM2 RAM1 RAM0
1024 bytes110
Setting prohibitedOther than above
1
1
32 Kbytes
40 Kbytes
0
0
0
1
0
0
0
0
16 Kbytes
24 Kbytes
1
1
0
1
0
0
512 bytes010
(2) Memory size switching register (IMS)
This register specifies the internal memory size. In principle, use IMS in a default status. However, when
using the external device expansion function with the
µ
PD78058, set IMS so that the internal ROM capacity
is 56 Kbytes or lower.
IMS is set with an 8-bit memory manipulation instruction.
RESET input sets this register to the value indicated in Table 22-3.
Figure 22-3. Memory Size Switching Register Format
Note The values after reset depend on the product. (See Table 22-3)
Table 22-3. Values when the Memory Size Switching Register is Reset
Part number Reset value
µ
PD78052, 78052Y 44H
µ
PD78053, 78053Y C6H
µ
PD78054, 78054Y C8H
µ
PD78055, 78055Y CAH
µ
PD78056, 78056Y CCH
µ
PD78058, 78058Y CFH