2
CAS
and 2
WE
Modes: The CAS/
WE
bit in RFSHCR can select two control modes for 16-bit-
wide DRAM: one using
UCAS
and
LCAS
; the other using
UW
and
LW
. These DRAM pins
correspond to H8/3048 Series pins as shown in table 7-6.
Table 7-6 DRAM Pins and H8/3048 Series Pins
DRAM Pin
H8/3048 Series Pin
CAS/
WE
= 0 (2
WE
Mode)
CAS/
WE
= 1 (2
CAS
Mode)
HWR
UW
UCAS
LWR
LW
LCAS
RD
CAS
WE
CS
3
RAS
RAS
Figure 7-5 (1) shows the interface timing for 2
WE
DRAM. Figure 7-5 (2) shows the interface
timing for 2
CAS
DRAM.
Figure 7-5 DRAM Control Signal Output Timing (1) (2
WE
Mode)
ø
( )
CS
RAS
3
( )
RD
CAS
( )
HWR
UW
( )
LWR
LW
RFSH
AS
Read cycle
Write cycle
Refresh cycle
*
Row
Column
Row
Column
Area 3 top address
Note: 16-bit access
*
Address
bus
160
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