H8SX1663 datasheet(327/1158 Pages) RENESAS

327 / 1158 page

Section 6 Bus Controller (BSC)

Rev.1.00 Jun. 07, 2006 Page 275 of 1102

REJ09B0294-0100

6.11.13

Refresh Control

This LSI includes a DRAM refresh control function. The refresh method is the auto-refresh. Self-

refresh cycles can be performed in software standby mode.

The refresh control function is enabled when area 2 is specified as the SDRAM space by the

DRAME and DTYPE bits in DRAMCR.

(1) Auto-Refresh Mode

Set the RFSHE bit in REFCR to 1 to select the auto-refresh.

An auto-refresh cycle is performed when the value set in RTCOR matches the RTCNT value

(compare match). RTCNT is an up-counter operated on the input clock specified bits RTCK2 to

RTCK0 in REFCR. RTCNT is initialized upon the compare match and restarts to count up with

H'00. Accordingly, an auto-refresh cycle is repeated at intervals specified by bits RTCK2 to

RTCK0 in RTCOR. Set the bits so that the required refresh intervals of the DRAM must be

satisfied.

Since setting bits RTCK2 to RTCK0 starts RTCNT to count up, set RTCNT and RTCOR before

setting bits RTCK2 to RTCK0. When changing RTCNT and RTCOR, the count operation should

be halted. When changing bits RTCK2 to RTCK0, change them only after disabling external bus

release and, if the write data buffer function is in use, disabling the write data buffer function and

reading the external space.

The external space cannot be accessed during auto-refresh.

H8SX1663 数据表(PDF) 327 Page - Renesas Technology Corp