r4f2456 Renesas Electronics Corporation., r4f2456 Datasheet - Page 297

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

Section 6 Bus Controller (BSC)
T
T
T
T
T
Rp
Rr
Rr1
Rcw
Rc2
φ
SDRAMφ
Address bus
Precharge-sel
RAS
CAS
WE
CKE
High
NOP
PALL
REF
Figure 6.68 Auto Refresh Timing
(TPC = 0, TPC0 = 0, RLW1 = 0, RLW0 = 1)
(2)
Self-Refreshing
A self-refresh mode (battery backup mode) is provided for synchronous DRAM as a kind of
standby mode. In this mode, refresh timing and refresh addresses are generated within the
synchronous DRAM.
To select self-refreshing, set the RFSHE bit to 1 in REFCR. When a SLEEP instruction is
executed to enter software standby mode, the SELF command is issued, as shown in figure 6.69.
When software standby mode is exited, the SLFRF bit in REFCR is cleared to 0 and self-refresh
mode is exited automatically. If an auto refresh request occurs when making a transition to
software standby mode, auto refreshing is executed, and then self-refresh mode is entered.
When using self-refresh mode, the OPE bit must not be cleared to 0 in SBYCR.
Rev. 1.00 Sep. 19, 2008 Page 267 of 1342
REJ09B0467-0100