188
(2) Self-Refresh
One of the DRAM standby modes is the self-refresh mode (battery backup mode), in which the
DRAM generates its own refresh timing and refresh address.
To select self-refresh, set the RFSHE bit and RMODE bits of the DRAMCR to 1. Next, execute a
SLEEP instruction to make a transition to software standby mode. As shown in Figure 7-29, the
CAS
and
RAS
signals are output and the DRAM enters self-refresh mode.
When you exit software standby mode, the RMODE bit is cleared to 0 and self-refresh mode is
exited.
When making a transition to software standby mode, self-refresh mode starts after a CBR refresh,
providing there is a CBR refresh request. CBR refresh requests occurring immediately before
entering software standby mode are cleared on completion of the self-refresh when the software
standby mode is exited.
T
Rp
ø
T
Rcr
CAS, LCAS
Software standby
T
Rc3
HWR (WE)
CSn (RAS)
Note: n= 2 to 5
High level
Figure 7-29 Self-Refresh Timing
Содержание H8S/2631
Страница 28: ...xviii Appendix G Package Dimensions 1154 ...
Страница 341: ...316 Transfer SAR or DAR DAR or SAR Block area First block Nth block Figure 9 8 Memory Mapping in Block Transfer Mode ...
Страница 918: ...905 ø DREQ0 DREQ1 tDRQS tDRQH Figure 25 19 DMAC DREQ Input Timing ...
Страница 955: ...943 A 2 Instruction Codes Table A 2 shows the instruction codes ...