r4f2456 Renesas Electronics Corporation., r4f2456 Datasheet - Page 269

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

(2)
A self-refresh mode (battery backup mode) is provided for DRAM as a kind of standby mode. In
this mode, refresh timing and refresh addresses are generated within the DRAM.
To select self-refreshing, set the RFSHE bit and SLFRF bit to 1 in REFCR. When a SLEEP
instruction is executed to enter software standby mode, the CAS and RAS signals are output and
DRAM enters self-refresh mode, as shown in figure 6.51.
When software standby mode is exited, the SLFRF bit is cleared to 0 and self-refresh mode is
exited automatically. If a CBR refresh request occurs when making a transition to software
standby mode, CBR 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 the SBYCR register.
Self-Refreshing
φ
A23 to A0
CS
AS
RD
HWR (WE)
RAS
CAS
Figure 6.50 Example of CBR Refresh Timing (CBRM = 1)
Normal space access request
Refresh period
Rev. 1.00 Sep. 19, 2008 Page 239 of 1342
Section 6 Bus Controller (BSC)
REJ09B0467-0100