Renesas SH7781 用户手册
12. DDR2-SDRAM Interface (DBSC2)
Rev.1.00 Jan. 10, 2008 Page 499 of 1658
REJ09B0261-0100
12.4.8
SDRAM Refresh Control Register 0 (DBRFCNT0)
The SDRAM refresh control register 0 (DBRFCNT0) is a readable/writable register. It is
initialized only upon power-on reset.
initialized only upon power-on reset.
16
17
18
19
20
21
22
23
24
25
26
27
28
29
31
30
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
ARFEN
⎯
⎯
⎯
⎯
⎯
⎯
⎯
⎯
⎯
⎯
⎯
⎯
⎯
⎯
⎯
R/W
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
BIt:
Initial value:
R/W:
0
1
2
3
4
5
6
7
8
9
10
11
12
13
15
14
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
SRFEN
⎯
⎯
⎯
⎯
⎯
⎯
⎯
⎯
⎯
⎯
⎯
⎯
⎯
⎯
⎯
R/W
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
BIt:
Initial value:
R/W:
Bit Bit
Name
Initial
Value R/W
Value R/W
Description
31 to 17
⎯
All 0
R
Reserved
These bits are always read as 0. The write value should
always be 0.
always be 0.
Operation when a value other than 0 is written is not
guaranteed.
guaranteed.
16
ARFEN
0
R/W
Auto-Refresh Enable Bit
Enables or disables automatic issue of auto-refresh.
The auto-refresh command is issued periodically
according to the settings of DBRFCNT1/2.
The auto-refresh command is issued periodically
according to the settings of DBRFCNT1/2.
For details on the auto-refresh command issue timing,
refer to section 12.5.5, Auto-Refresh Operation.
refer to section 12.5.5, Auto-Refresh Operation.
0: Disables automatic issue of auto-refresh.
1: Enables automatic issue of auto-refresh.
15 to 1
⎯
All 0
R
Reserved
These bits are always read as 0. The write value should
always be 0.
always be 0.
Operation when a value other than 0 is written is not
guaranteed.
guaranteed.