HD6417021 Hitachi Semiconductor, HD6417021 Datasheet - Page 154

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

8.5.3
Precharge State Control: When the microprocessor clock frequency is raised and the cycle
period shortened, 1 cycle may not always be sufficient for the precharge time for the RAS signal
when the DRAM is accessed. The BSC allows the precharge cycle to be set to 1 state or 2 states
using the RAS signal precharge cycles bit (TPC) of the DCR. When the TPC bit is 0, the
precharge cycle is 1 state; when TPC is 1, the precharge cycle is 2 states. Figure 8.19 shows the
timing when the precharge cycle is 2 states.
138 HITACHI
Read
Write
Wait State Control
WRH, WRL
WRH, WRL
AD15–AD0
AD15–AD0
A21–A0
RAS
CAS
CK
Figure 8.18 Long Pitch Access Timing
T
p
Row address
T r
T
c
1
Column address
T
c
2