Rev.6.00 Oct.28.2004 page 118
of 1016
REJ09B0138-0600H
6.2.7
DRAM Control Register (DRAMCR)
Bit
:
7
6
5
4
3
2
1
0
RFSHE
RCW
RMODE
CMF
CMIE
CKS2
CKS1
CKS0
Initial value :
0
0
0
0
0
0
0
0
R/W
:
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
DRAMCR is an 8-bit readable/writable register that selects the DRAM refresh mode and refresh counter clock, and
controls the refresh timer.
DRAMCR is initialized to H'00 by a power-on reset and in hardware standby mode. It is not initialized by a manual reset*
or in software standby mode.
Note:
* Manual reset is only supported in the H8S/2357 ZTAT.
Bit 7—Refresh Control (RFSHE): Selects whether or not refresh control is performed. When refresh control is not
performed, the refresh timer can be used as an interval timer.
Bit 7
RFSHE
Description
0
Refresh control is not performed
(Initial value)
1
Refresh control is performed
Bit 6—RAS-CAS Wait (RCW): Controls wait state insertion in DRAM interface CAS-before-RAS refreshing.
Bit 6
RCW
Description
0
Wait state insertion in CAS-before-RAS refreshing disabled
(Initial value)
RAS
falls in T
Rr
cycle
1
One wait state inserted in CAS-before-RAS refreshing
RAS
falls in T
Rc1
cycle
Bit 5—Refresh Mode (RMODE): When refresh control is performed (RFSHE = 1), this bit selects whether normal
refreshing (CAS-before-RAS refreshing for the DRAM interface) or self-refreshing is performed.
Bit 5
RMODE
Description
0
DRAM interface
CAS-before-RAS refreshing used
(Initial value)
1
Self-refreshing used
Bit 4—Compare Match Flag (CMF): Status flag that indicates a match between the values of RTCNT and RTCOR.
When refresh control is performed (RFSHE = 1), 1 should be written to the CMF bit when writing to DRAMCR.
Bit 4
CMF
Description
0
[Clearing condition]
Cleared by reading the CMF flag when CMF = 1, then writing 0 to the CMF flag
(Initial value)
1
[Setting condition]
Set when RTCNT = RTCOR
Содержание ZTAT H8S/2357F
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