DMP Electronics eBOX-3350MX-AP Uživatelský manuál stáhnout pdf (Strana 25)

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

DM&P M6117D : System on a chip

Page 24

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

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

4.3.5 How to remap memory to top of memory

The address 0C0000h ~ 0FFFFFh is for ROM or reserved area. When this range of RAM is not used as shadow RAM, then

the memory is wasted. However, we can use this area of RAM by remapping the higher address to the non-shadow RAM.

In order to have continuous memory mapping, the remapping address selects the higher area to do so. For example, if we

have 12MB DRAM on board, shadow RAM all disabled, then we can select 13MB (00D00000h) to be the address to remap.

There are two remapping types determined by D[1] of index 11h, split (D[1]=0) and move-out (D[1]=1). By programming

D[7-4] of index 12h, we can set the split address A23-A20. Memory split remapping can be disabled by programming index

11h : D[2] to 0. Please notice that index 11h : D[2] must be set to 1 and index 11h : D[1] must be set to 0 if you want to

enable split remap. Otherwise, the move-out remap is selected when index 11h: D[1] is set to 1. Following are the different

cases of memory remapping.

(A) No shadow, split address[23-20] = A[23-20], Remap type = split remap

A19 A18 A17 A16 PA23 PA22 PA21 PA20 PA19 PA18 PA17

0 0 0 x 0 0 0 0 1 0 1

0 0 1 x 0 0 0 0 1 1 0

0 1 0 x 0 0 0 0 1 1 1

N40000h

N20000h

N00000h

100000h

0E0000h

0C0000h

0A0000h

000000h

N.384 MB

N.256MB

N.128MB

Page EF

Page CD

Page AB

Remap split

address to page

ABCDEF

where N < 0Fh

(B) Shadow Page EF, split address[23-20] = A[23-20], Remap type = split remap

A19 A18 A17 A16 PA23 PA22 PA21 PA20 PA19 PA18 PA17

0 0 0 x 0 0 0 0 1 0 1

0 0 1 x 0 0 0 0 1 1 0

N20000h

N00000h

100000h

0E0000h

0C0000h

0A0000h

000000h

N.256 MB

N.128MB

Shadow EF

Page CD

Page AB

Remap split

address to page

ABCD

where N < 0Fh

1 2 ... 20 21 22 23 24 25 26 27 28 29 30 ... 111 112

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