150
H8S/2678 Series chip
(Address shift size
set to 10 bits)
RAS
n (
CS
n)
2-CAS type 16-Mbit DRAM
1-Mbyte
×
16-bit configuration
10-bit column address
RAS
UCAS
UCAS
LCAS
LCAS
HWR
(
WE
)
WE
RD
(
OE
)
OE
A9
A8
A10
A9
A8
A7
A7
A6
A6
A5
A5
A4
A4
A3
A3
A2
A2
A1
A1
A0
D15 to D0
D15 to D0
Row address input:
A9 to A0
Column address input:
A9 to A0
Figure 4.28 Example of 2-CAS DRAM Connection
4.5.12
Burst Operation
With DRAM, in addition to full access (normal access) in which data is accessed by outputting a
row address for each access, a fast page mode is also provided which can be used when making
consecutive accesses to the same row address. This mode enables fast (burst) access of data by
simply changing the column address after the row address has been output. Burst access can be
selected by setting the BE bit to 1 in DRAMCR.
Burst Access (Fast Page Mode) Operation Timing: Figures 4.29 and 4.30 show the operation
timing for burst access. When there are consecutive access cycles for DRAM space, the
CAS
signal and column address output cycles (two states) continue as long as the row address is the
same for consecutive access cycles. The row address used for the comparison is set with bits
MXC2 to MXC0 in DRAMCR.
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