DMP Electronics eBOX-3350MX-AP Bedienungsanleitung PDF herunterladen (Seite 24)

Jan Yin Chan Electronics Co.,LTD. 386SX Single Chip PC

M6117D : System on a chip

DM&P

Jan Yin Chan Electronics Co,. LTD. M6117D 386SX Single Chip PC Page 23

8F-1,No.22,Wuchyuan 2RD.,Hsin Chuang city Taipei Hsien, Taiwan, R.O.C. Tel: 886-(02) 2298-0770 Fax: (02) 2299-1883

4.3.4 DRAM refreshing

DRAM refresh cycle is 256 for every 4ms. However, for some DRAM products, the data at capacitance can be maintained

more than 15 us. To get higher system performance, we can slow down refresh period for some DRAM products. By

programming index 36h : D[5-4], we can get slow refresh period as follows:

Index 36h : D[5]

D[4] Refresh period setting

0 0 15 us

0 1 120 us

1 0 15 us

1 1 60 us

We also support three types of DRAM refresh :

(A) RAS only refresh

This kind of refresh will be selected if D[1] of index 10h is set to ‘0’ (low)

don’t care ROW

RASJ

CASJ

don’t care

Refresh ROW address

(B) CAS before RAS refresh

This kind of refresh will be selected if D[1] of index 10h is set to ‘1’ (high)

don’t ca

RASJ

CASJ

pre

: RAS precharge time

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DMP Electronics eBOX-3350MX-AP Bedienungsanleitung Seite 24