SDRAM Interface Functional Overview
Memory Banks and Pages
Copyright © 2002 Marvell
CONFIDENTIAL
Doc. No. MV-S300165-00, Rev. A
May 21, 2002, Preliminary
Document Classification: Proprietary Information
Page 43
Figure 15: Two Read Interleaving from Different Virtual Banks
•
Cycle 2: Bank0 - Row activating.
•
Cycle 4: Column cycle (command).
•
Cycle 6: Row activating.
•
Cycle 7: Fetch first data (CL = 3 cycles).
•
Cycle 8: Column cycle (command).
•
Cycle 10: Precharge (close bank).
•
Cycle 11: Fetch first data (CL = 3 cycles).
In addition, the SDRAM controller supports open pages. This means DRAM pages can stay open. The controller
supports up to 16 open pages - one per each virtual bank. Each ROW address in the SDRAM defines a page and
the COLUMN selects the data in the current open page. When a page is kept open at the end of a burst (no pre-
charge cycle) and if the next cycle to the same virtual bank hits the same page (same row address), there is no
need for a new activate cycle. To enable open pages, set the SDRAM Bankx Parameters register’s
OpenP
bits
[3:0], at offset 0x44c, 0x450, 0x454 and 0x458 to ‘1’.
The figure below shows a single read access to a non-open page when the open pages are disabled.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
0x0000
D00 D01 D02 D03 D10 D11 D12 D13
0ns
50ns
100ns
150ns
TCLK
DAdr[12:0]
SDQM*
SDATA
SRAS*
SCAS*
DWr*