
APPLICATION
2.6 Processor mode
2-68
3802 GROUP USER’S MANUAL
_____
(2) Application example of memory expansion in the case where the
(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 P3
2
/
ONW
pin while the CPU is in the read or write status,
the read or write cycle corresponding to 1 cycle of
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 0000
to 0007
16
and addresses 0440
16
to FFFF
16
.
Figure 2.6.7 shows an application example of the
function.
is extended. In the extended period,
____
Fig. 2.6.7 Application example of the
ONW
function
3802 group
CNV
SS
AD
15
8
P5
8
P6
ONW
AD
14
–
AD
0
DB
0
–
DB
7
RD
WR
M5M27C256AK-10
M5M5256BP-10
CE
A
0
–A
14
D
0
–D
7
OE
A
0
–A
14
DQ
1
–DQ
8
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)
0000
16
8000
16
0440
16
0040
16
0008
16
FFFF
16
Memory map
74F04
S
15
8
8
P4
2
P3
0
, P3
1
EPROM
SRAM