r4f2426 Renesas Electronics Corporation., r4f2426 Datasheet - Page 291

• Manufacturer Part Number: r4f2426
• Description: 16-bit Single-chip Microcomputer H8s Family / H8s/2400 Series
• Manufacturer: Renesas Electronics Corporation.

Section 6 Bus Controller (BSC)
T Rp
T Rr
T Rc1
T Rc2
φ
SDRAMφ
Address bus
Precharge-sel
RAS
CAS
WE
CKE
High
PALL
REF
NOP
Figure 6.66 Auto Refresh Timing
When the interval specification from the PALL command to the REF command cannot be
satisfied, setting the RCW1 and RCW0 bits of REFCR enables one to three wait states to be
inserted after the T
cycle that is set by the TPC1 and TPC0 bits of DRACCR. Set the optimum
Rp
number of waits according to the synchronous DRAM connected and the operating frequency of
this LSI. Figure 6.67 shows the timing when one wait state is inserted. Since the setting of bits
TPC1 and TPC0 of DRACCR is also valid in refresh cycles, the command interval can be
extended by the RCW1 and RCW0 bits after the precharge cycles.
Rev. 1.00 Sep. 19, 2008 Page 263 of 1270
REJ09B0466-0100