UPD784044 Datasheet, PDF (49/90 Pages) NEC – 16-BIT SINGLE-CHIP MICROCONTROLLER

µPD784044(A), 784046(A)
9.2 Memory Space
The 1M-byte memory space is divided into the following eight spaces of logical addresses. Each space can
be controlled by using the programmable wait function and bus sizing function.
Figure 9-2. Memory Space
FFFFFH
512K bytes
8 0 0 0 0H
7 F F F FH
4 0 0 0 0H
3 F F F FH
2 0 0 0 0H
1 F F F FH
1 0 0 0 0H
0 F F F FH
0C0 0 0H
0BFFFH
0 8 0 0 0H
0 7FFFH
0 4 0 0 0H
0 3FFFH
9.3 Programmable Wait
0 0 0 0 0H
256K bytes
128K bytes
64K bytes
16K bytes
16K bytes
16K bytes
16K bytes
A wait state can be inserted to each of the eight memory spaces while the RD, LWR, and HWR signals are
active. Even if memories with different access times are connected, therefore, the overall efficiency of the system
is not degraded.
In addition, an address wait function that extends the active period of the ASTB signal is also available to
extend the address decode time (this function can be set to all the spaces).
9.4 Bus Sizing Function
The µPD784046(A) can change the external data bus width between 8 and 16 bits when an external device
is connected. Even if the memory space is divided by eight, the bus width of each memory space can be specified
independently.
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