SH7261 datasheet(301/1348 Pages) RENESAS

301 / 1348 page

Section 9 Bus State Controller (BSC)

Rev. 2.00 Sep. 07, 2007 Page 269 of 1312

REJ09B0320-0200

(b)

Procedure for Transition to and Recovery from Self-Refresh Mode

Figure 9.27 shows the procedure for transitioning to and recovering from self-refresh mode.

Self-refresh mode

Initialization sequence

(1) Halt any DMA access to SDRAM area

(2) Halt access to all SDRAMC channels (EXENB = 0) by means of program

assigned to other than SDRAM area

(3) Confirm that EXENB has been cleared to 0

Start self-refresh

(1) Confirm that all status bits in SDSTR have been cleared to 0

(2) Set DSFEN bit to 1 by means of program assigned to other than SDRAM area

End self-refresh

(1) Confirm that all status bits in SDSTR have been cleared to 0

(2) Clear DSFEN bit to 0 by means of program assigned to other than SDRAM

area

Access enabled status

(DRFEN = 1, EXENB = 1)

Enable access

Enable access to SDRAMC (EXENB = 1) by means of program assigned to other

than SDRAM area

Access enabled status

(DRFEN = 1, EXENB = 1)

Figure 9.27 Procedure for Transition to and Recovery from Self-Refresh Mode

Note:

Before transitioning to or recovering from self-refresh mode it is necessary to halt

SDRAM access to the affected channels. Consequently, it is not possible to transition to or

recover from self-refresh mode while programs or DMA operations that access SDRAM

are in progress. Pay attention to the following points when writing programs.

• Before transitioning to self-refresh mode, halt any DMA channel transfers that access

the SDRAM area of the affected channels.

• Make sure that programs run while transitioning to self-refresh mode, while in self-

refresh mode, or while recovering from self-refresh mode do not access operands or

fetch (or pre-fetch) instructions stored in the SDRAM area.

SH7261 Datasheet(PDF) 301 Page - Renesas Technology Corp