H8SLASH3028F datasheet(196/923 Pages) RENESAS

196 / 923 page

Rev. 2.00, 09/03, page 166 of 890

To use the self-refresh function, set the SRFMD bit to 1 in DRCRA. When a SLEEP instruction is

subsequently executed in order to enter software standby mode, the

CAS and RAS signals are

output and the DRAM enters self-refresh mode, as shown in figure 6.30.

When the chip exits software standby mode,

CAS and RAS outputs go high.

The following conditions must be observed when the self-refresh function is used:

• When burst access is selected, RAS up mode must be selected before executing a SLEEP

instruction in order to enter software standby mode. Therefore, if RAS down mode has been

selected, the RDM bit in DRCRA must be cleared to 0 and RAS up mode selected before

executing the SLEEP instruction. Select RAS down mode again after exiting software standby

mode.

• The instruction immediately following a SLEEP instruction must not be located in an area

designated as DRAM space.

The self-refresh function will not work properly unless the above conditions are observed.

CSn (RAS)

Address bus

4 (UCAS)

5 (LCAS)

RD (WE)

RFSH

Software standby

mode

Oscillation stabilization

time

High-impedance

Figure 6.30 Self-Refresh Timing (CSEL = 0)

Refresh Signal (

RFSH

RFSH): A refresh signal (RFSH) that transmits a refresh cycle off-chip can be

output by setting the RFSHE bit to 1 in DRCRA.

RFSH output timing is shown in figures 6.28,

6.29, and 6.30.

H8/3028F 数据表(PDF) 196 Page - Renesas Technology Corp