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CHAPTER 27
µ
PD78F4225 AND
µ
PD78F4225Y PROGRAMMING
User’s Manual U12697EJ3V0UM
27.1 Internal Memory Size Switching Register (IMS)
IMS is a register to prevent a certain part of the internal memory from being used by software. By setting the IMS,
it is possible to establish a memory map that is the same as the mask ROM product's memory map for the internal
memory (ROM, RAM) which has a different capacity.
IMS is set by an 8-bit memory manipulation instruction.
RESET input sets IMS to FFH.
Figure 27-1. Format of Internal Memory Size Switching Register (IMS)
IMS
1
7
6
5
4
3
2
1
1
ROM1
ROM0
1
1
RAM1
0
RAM0
Address: 0FFFCH
W
After reset: FFH
Symbol
ROM1
ROM0
1
0
96 KB
128 KB
Setting prohibited
1
1
Other than above
Setting prohibited
Other than above
Internal ROM capacity selection
RAM1
RAM0
1
0
3,072 bytes
3,840 bytes
1
1
Internal high-speed RAM capacity selection
Caution The IMS is not available for mask ROM versions (
µ
PD784224, 784225, 784224Y, and 784225Y).
The IMS settings to create the same memory map as mask ROM versions is shown in Table 27-2.
Table 27-2. Internal Memory Size Switching Register (IMS) Settings
Relevant Mask ROM Version
IMS Setting
µ
PD784224, 784224Y
EEH
µ
PD784225, 784225Y
FFH
