r4f2456 Renesas Electronics Corporation., r4f2456 Datasheet - Page 270

• Manufacturer Part Number: r4f2456
• Description: 16-bit Single-chip Microcomputer H8s Family / H8s/2400 Series
• Manufacturer: Renesas Electronics Corporation.

Section 6 Bus Controller (BSC)
In some DRAMs provided with a self-refresh mode, the RAS signal precharge time immediately
after self-refreshing is longer than the normal precharge time. A setting can be made in bits
TPCS2 to TPCS0 in REFCR to make the precharge time immediately after self-refreshing from 1
to 7 states longer than the normal precharge time. In this case, too, normal precharging is
performed according to the setting of bits TPC1 and TPC0 in DRACCR, and therefore a setting
should be made to give the optimum post-self-refresh precharge time, including this time. Figure
6.52 shows an example of the timing when the precharge time immediately after self-refreshing is
extended by 2 states.
Rev. 1.00 Sep. 19, 2008 Page 240 of 1342
REJ09B0467-0100
φ
CSn (RASn)
UCAS, LCAS
HWR (WE)
Note: n = 2 to 5
T
Rp
Figure 6.51 Self-Refresh Timing
T
Rr
High
Software
standby
T
Rc3