UPD784026 Renesas Electronics Corporation., UPD784026 Datasheet - Page 89

• Manufacturer Part Number: UPD784026
• Description: 16/8-bit Single-chip Microcontrollers
• Manufacturer: Renesas Electronics Corporation.

3.6
different from that of the PD784025. In order to mask this difference, the PD78P4026 has a function (the memory size
switching function) which prevents part of the internal memory from being used in software.
map as in the PD784025, this register must be written to immediately after a reset. Do not change the written value.
in the PD784025 or PD784026 will not affect the operation of the device.
The PD78P4026 incorporates 64 K-byte internal ROM and 2048-byte internal RAM, and its memory map is therefore slightly
Memory size switching is performed by means of the internal memory size switching register (IMS). To set the same memory
The IMS can be written to with an 8-bit manipulation instruction. The IMS format is shown in Figure 3-6.
RESET input sets the IMS register to FFH.
The IMS register is not provided in the PD784025 and PD784026, but executing an instruction that writes to IMS register
Caution If the PD78P4026 is selected by the in-circuit emulator as the emulation CPU, the memory size is always
PD78P4026 MEMORY MAPPING
IMS
the same as that of the PD784026 even if an instruction that writes data other than FFH (EFH) to IMS is
executed.
IMS7
7
IMS6
6
Figure 3-6 Internal Memory Size Switching Register (IMS) Format
IMS5
5
IMS4
4
CHAPTER 3 CPU ARCHITECTURE
IMS3
3
IMS2
2
IMS1
1
IMS0
0
IMS0-7 Memory Size
FFH
EFH
0FFFCH
Address
Same as PD784026
Same as PD784025
On reset
FFH
R/W
R/W
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