HD6417034B RENESAS [Renesas Technology Corp], HD6417034B Datasheet - Page 179

• Manufacturer Part Number: HD6417034B
• Description: 32-Bit RISC Microcomputer
• Manufacturer: RENESAS [Renesas Technology Corp]

8.5.5
In addition to the normal mode of DRAM access, in which row addresses are output at every
access and data then accessed (full access), the DRAM also has a high-speed page mode for use
when continuously accessing the same row. The high speed page mode enables fast access of data
simply by changing the column address after the row address is output (burst mode). Select
between full access and burst operation by setting the burst enable bit (BE) in DCR. When the BE
bit is set to 1, burst operation is performed when the row address matches the previous DRAM
access row address. Figure 8.22 shows a comparison between full access and burst operation.
Short pitch high-speed page mode or long pitch high-speed page mode burst transfers can be
selected independently for DRAM read/write cycles even when burst operation is selected by
using the bits corresponding to area 1 in WCR1 and WCR2 (RW1, WW1, DRW1, DWW1). RAS
down mode or RAS up mode can be selected by setting the RAS down bit (RASD) in DCR when
there is an access outside the DRAM space during burst operation.
A21–A0
A21–A0
AD15–
AD15–
RAS
CAS
RAS
CAS
AD0
AD0
DRAM Burst Mode
Row address 1
Row address 1
Figure 8.22 Full Access and Burst Operation
(b) Burst operation (read cycle)
(a) Full access (read cycle)
address 1
Column
address 2
Column address 1
Data 1
Data 1
Column
Rev. 7.00 Jan 31, 2006 page 153 of 658
Row address 2
address 3
Data 2
Column
Section 8 Bus State Controller (BSC)
address 4
Data 3
Column
REJ09B0272-0700
Data 2
Data 4
address 2
Column