SH7708 datasheet(286/633 Pages) RENESAS

286 / 633 page

268

Self-refreshing is performed in normal operation, in sleep mode, in standby mode, and in a manual

reset.

CKIO

CKE

CSn

RAS

CASxx

TRs1

(TRs2)

TRs3

(Tpc)

RD/

Figure 10.31 Synchronous DRAM Self-Refresh Timing

3. Relationship between refresh requests and bus cycle requests

If a refresh request is generated during execution of a bus cycle, execution of the refresh is

deferred until the bus cycle is completed. If a refresh request occurs when the bus has been

released by the bus arbiter, refresh execution is deferred until the bus is acquired. If a match

between RTCNT and RTCOR occurs while a refresh is waiting to be executed, thereby generating

a new refresh request, the previous refresh request is eliminated. To perform normal refreshing,

ensure that no bus cycle or bus mastership occurs that is longer than the refresh interval. When a

refresh request is generated, the

IRQOUT pin is asserted (driven low). Therefore, normal

refreshing can be performed by having the

IRQOUT pin monitored by a bus master other than the

SH7708 Series requesting the bus, or the bus arbiter, and returning the bus to the SH7708 Series.

When refreshing is started, and if no other interrupt request has been generated, the

IRQOUT pin

is negated (driven high).

SH7708 Datenblatt(PDF) 286 Page - Renesas Technology Corp