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16
µ
PD78F4225Y
5. INTERNAL MEMORY SIZE SELECT REGISTER (IMS)
The IMS is a register that prevents by software a part of the internal memory from being used. By using this
register, the memory of the
µ
PD78F4225Y can be mapped in the same manner as a mask ROM model with different
internal memory (ROM and RAM) capacity.
This register is set by using an 8-bit memory manipulation instruction.
Its value is set to FFH by RESET input.
Figure 5-1. Format of Internal Memory Size Select Register (IMS)
Caution
IMS is not provided on the mask ROM models (
µ
PD784224Y and 784225Y).
The value to be set to the IMS to map the memory of the
µ
PD78F4225Y in the same manner as the mask ROM
model is shown in Table 5-1.
Table 5-1. Set Value of Internal Memory Size Select Register (IMS)
Mask ROM Model
Set Value of IMS
µ
PD784225Y
EEH
µ
PD784226Y
FFH
1
1
ROM1
ROM0
1
1
RAM1
RAM0
7
6
5
4
3
2
1
0
ROM1
0
0
1
1
ROM0
0
1
0
1
Selects internal ROM capacity
48K bytes
64K bytes
96K bytes
128K bytes
RAM1
0
0
1
1
RAM0
0
1
0
1
Selects peripheral RAM capacity
1536 bytes
2304 bytes
3072 bytes
3840 bytes
Address: 0FFFCH
IMS
At reset: FFH
W
Summary of Contents for uPD78F4225Y
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