HD6417021 Hitachi Semiconductor, HD6417021 Datasheet - Page 163

• Manufacturer Part Number: HD6417021
• Description: SuperH RISC engine
• Manufacturer: Hitachi Semiconductor

• RAS Up Mode: When the RASD bit is cleared to 0, the RAS signal reverts to high whenever a
AD15–
A21–
DRAM access pauses for access to another space. Burst operation continues only while
DRAM access is continuous. Figure 8.28 shows the timing when an external memory space
access occurs during burst operation in the RAS up mode.
RAS
CAS
AD0
WR
CK
A0
T
p
Row address
T r
DRAM access
address 1
Column
Figure 8.27 RAS Down Mode
T
c
Data 1
address 2
Column
T
c
External memory
Data 2
space access
External
memory
memory data
T1
External
address 3
Column
DRAM access
T
c
Data 3
address 4
Column
T
c
HITACHI 147
Data 4