Technical information

APPLICATION
2.4 Processor mode
2-53
3800 GROUP USER’S MANUAL
(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.
____
Fig. 2.4.7 Application example of the ONW function
3800 group
CNV
SS
AD15
8
P5
8
P6
ONW
AD14
AD0
DB0
DB7
RD
WR
M5M27C256AK-10
M5M5256BP-10
CE
A0–A14
D0–D7
OE
A0–A14
DQ1–DQ8
OE W
8MHz V CC = 5.0V ± 10 %
External RAM area
(M5M5256BP)
SFR area
Internal RAM area
External RAM area
(M5M5256BP)
External ROM area
(M5M27C256AK)
000016
800016
044016
004016
000816
FFFF16
Memory map
74F04
S
–
15
8
8
P4
2
P3
0, P31
EPROM SRAM
–
2
P7