HD6412350 Hitachi, HD6412350 Datasheet - Page 188

• Manufacturer Part Number: HD6412350
• Description: (HD6412350 / HD6432351) 16-BIT MICROCONTROLLER
• Manufacturer: Hitachi

6.5.10
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 a
number of 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 in MCR to 1.
(1) Burst Access (Fast Page Mode) Operation Timing
Figure 6-20 shows 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 MXC1 and MXC0 in MCR.
The bus cycle can also be extended in burst access by inserting wait states. The wait state insertion
method and timing are the same as for full access. For details, see section 6.5.8, Wait Control.
168
Read
Write
Note: n = 2 to 5
Burst Operation
CAS, LCAS
Figure 6-20 Operation Timing in Fast Page Mode (2-WE System)
CSn (RAS)
HWR (WE)
HWR (WE)
D
D
A
15
15
23
to A
to D
to D
ø
0
0
0
T
p
row
T
r
T
c1
column1
T
c2
T
c1
column2
T
c2