Renesas SH7781 - Manual (Page 551)

12. DDR2-SDRAM Interface (DBSC2)
Rev.1.00 Jan. 10, 2008 Page 521 of 1658
REJ09B0261-0100
LV1TH
LV0TH
0
Time
Refresh counter
value
Max. value
(Average refresh interval
+ LV1TH)
Level 1
(Refreshing during
request empty cycles)
Level 0
(Refreshing in vacant
periods between
SHwy commands)
Level 2
(Refreshing not done)
Refreshing is done immediately
after auto-refresh is enabled Refreshing is done in
vacant periods between
SHwy commands
Refreshing is done
during request
empty cycles
The counter value increments
by the amount of
the average refresh interval
Figure 12.7 Relation between Auto-Refresh Operation and Threshold Values
12.5.6 Regarding Address Multiplexing
Memory of various sizes can be connected through the settings of the SDRAM configuration
register (DBCONF). The BWIDTH bits are used to set the external data bus width, and the SPLIT
bit is used to set the size of the memory connected. The BASFT bit setting is used to move the
position of the bank address toward the lower bits; depending on the application the possibility of
page hits may be increased.