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CHAPTER 23
µ
PD78F0354, 78F0354Y
User’s Manual U15798EJ2V0UD
23.1 Memory Size Switching Register
The
µ
PD78F0354 and 78F0354Y allow users to select the internal memory capacity using the memory size
switching register (IMS) so that the same memory map as that of mask ROM versions with a different internal memory
capacity can be achieved.
IMS is set by an 8-bit memory manipulation instruction.
RESET input sets the value of this register to CFH.
Caution Be sure to set IMS to C8H, 46H, or 48H as the initial setting of the program. Reset input initializes
IMS to CFH. Be sure to set IMS to C8H, 46H, or 48H after reset.
Figure 23-1. Format of Memory Size Switching Register (IMS)
Address: FFF0H After reset: CFH R/W
Symbol
7
6
5
4
3
2
1
0
IMS
RAM2
RAM1
RAM0
0
ROM3
ROM2
ROM1
ROM0
RAM2
RAM1
RAM0
Internal high-speed RAM capacity selection
0
1
0
512 bytes
1
1
0
1,024 bytes
Other than above
Setting prohibited
ROM3
ROM2
ROM1
ROM0
Internal ROM capacity selection
0
1
1
0
24 KB
1
0
0
0
32 KB
Other than above
Setting prohibited
The IMS settings to obtain the same memory map as mask ROM versions are shown in Table 23-2.
Table 23-2. Memory Size Switching Register Settings
Target Mask ROM Versions
IMS Setting
µ
PD780343, 780353, 780343Y, 780353Y
46H
µ
PD780344, 780354, 780344Y, 780354Y
48H
Caution When using the mask ROM versions, be sure to set the value indicated in Table 23-2 to IMS.
Содержание mPD780344 Series
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