UPD784026 Renesas Electronics Corporation., UPD784026 Datasheet - Page 615

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

21.1.2 Memory Map with External Memory Extension
addresses as the internal ROM area, internal RAM area and SFR area (excluding the external SFR area (0FFD0H to
0FFDFH)) cannot be accessed. If an access is made to these addresses, the memory or SFR in the PD784026 has access
priority and no ASTB signal, RD signal or WR signal is output (these pins remain at the inactive level). The address bus
output level remains at the level output prior to this, and the address/data bus output becomes high-impedance.
by the program masked.
The memory map when memory extension is used is shown in Figures 21-2 to 21-5. External devices at the same
Except in 1M-byte extension mode, the address output externally is output with the upper part of the address specified
Example 1:
In 256-byte extension mode, when address 54321H is accessed by the program, the output address is 21H.
Example 2:
In 256-byte extension mode, when address 67821H is accessed by the program, the output address is 21H.
CHAPTER 21 LOCAL BUS INTERFACE FUNCTION
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