M38002M4 Datasheet, PDF (101/173 Pages) Mitsubishi Electric Semiconductor – 8-BIT SINGLE-CHIP MICROCOMPUTER

APPLICATION
2.4 Processor mode
(2) Application example of memory expansion in the case where the ONW (One-Wait)
function is used
Outline : ONW function is used when the external memory access is slow.
If “L” level signal is input to the P32/ONW pin while the CPU is in the read or write status,
the read or write cycle corresponding to 1 cycle of φ is extended. In the extended period,
the RD or WR signal is kept at the “L” level. The ONW function operates only when data is
read from or written into addresses 000016 to 000716 and addresses 044016 to FFFF16.
Figure 2.4.7 shows an application example of the ONW function.
3800 group
CNVSS
AD15
2 P30, P31
ONW
74F04
M5M27C256AK-10
CE
M5M5256BP-10
S
8 P4
AD14
15
AD0
A0–A14
EPROM
A0–A14
SRAM
8 P5
8 P6
2 P7
DB0
DB7
8
D0–D7
OE
RD
WR
8MHz VCC= 5.0V ± 10 %
DQ1–DQ8
OE W
Memory map
000016 _{External RAM area}
(M5M5256BP)
000816 _{SFR area}
004016 Internal RAM area
044016 _{External RAM area}
(M5M5256BP)
800016
External ROM area
(M5M27C256AK)
FFFF16
____
Fig. 2.4.7 Application example of the ONW function
3800 GROUP USER’S MANUAL
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